CHAPTER V. General Characteristics

GENERAL CHARACTERISTICS

The general form of the platypus is by now familiar to all. It appears stuffed and mounted in all natural history museums, and illustrations of it adorn all ordinary natural history books. Yet, strange as it may seem, I have never seen a correctly mounted specimen in a museum, nor a correct figure of the whole animal in a book.

The most conspicuous feature about the bodily form of the platypus is its prevailing flatness. The naked muzzle is broad and flat; the head is so much depressed that the eyes have become more dorsal than lateral in position; the trunk is broad and flat, though in profile its outline rises from the shoulders to a point a little behind the middle of its length, and then falls towards the tail; a cross-section has the form of a low arch, a good deal more broad than high; finally, the tail is broad and flat, with a broadly rounded tip.

The skin, kimono-like, is over-large for the size of the body, and, except at all the animal’s extremities, it appears to be entirely dissociated from the primary nervous system. That is to say, a platypus will readily respond to the slightest touch on either feet, paws, bill, lips, or tail, but will not shrink from being soothingly stroked, from forehead to rump, along the fur. This characteristic is most apparent while the animal is submerged in water, where it is unable to see, hear, or smell the experimentalist.

In this instance the eyes, which are situated above the white patches, are closed.

Plate 8]

Note how sides of lower lip are pressed tightly against upper jaws, leaving space in centre for sucking in foodstuff.

Plate 8]

The muzzle with its backward-projecting flaps is naked, as also are the upper surfaces of the digits of paws and feet, and the palms and soles. All the rest of the body is covered with hair, which is of two main kinds. Closely investing all the body except the tail and extremities of the limbs is a fine dense under-fur, beyond which project the ends of a much longer and harsher kind of hair, with highly polished tips. The under-fur is woolly, grey at the base, inclining to brownish at the outer ends. The longer hairs are remarkable in that their projecting portions are flattened, giving them a lance-like appearance, and are generally curved so that the ends turn in to the fur. On the animal’s back and sides these hairs are usually dark brown in colour, but the tips are frequently silvery white, or, in reddish individuals, golden yellow. The prevailing paler colour of the under surface is due to the absence of dark pigment from the ends of these hairs, which have grey basal portions and tips ranging from silver-white through yellow to chestnut and (in some cases) deep ferruginous brown.

This longer fur determines the animal’s colour, which is variable within fairly narrow limits. The usual coloration is deep umber-brown on the back and sides of head and body and upon the exposed surfaces of the limbs; but reddish individuals are not uncommon, and some examples are almost black. The ends of the long hairs are frequently curly, and the prevailing ground-colour becomes powdered, as it were, with silver or gold, in consequence of the different colour of the tips.

The hair on the dorsal surface of the tail is coarse, and without flattened tips. Owing to the constant dragging of the under-side over the ground, this surface is usually denuded of hair, but in young individuals a delicate silky fur is present, usually of a golden colour, but ranging to warm brown.

The ventral surface of the body is described by Thomas (1888, p. 389) as ‘dirty greyish white’, which hardly does justice to the beauty of the fur on this part. It ranges from silver through yellow to warm chestnut, being lightest on the chest and throat, and darkening posteriorly. Old males sometimes have the whole ventral surface a warm brown in colour, with darker markings about the chin, limbs, and vent. The colour is, in all instances, due to the highly polished tips of the longer hairs, which have a brilliant sheen comparable with that of the breast-feathers of the tippet grebe (see Plate 7). An albino is recorded by Bennett, and one is exhibited in the Mammal Gallery of the Australian Museum, Sydney. Sometimes, too, the black skin of the extremities is mottled with white.

The coat of the platypus is devoid of stripes, bars, spots, or pattern of any description, save for a small yellowish-white to yellowish-brown spot placed just beneath the eye. Bennett (1860, p. 98) correctly described this spot, and noted that it occurred, with a single exception, in all specimens of either sex which had come under his observation. Thomas (1888, p. 389) dismisses it briefly as ‘a spot round each eye white or yellowish.’ Wood Jones (1923, p. 46) remarks--“There is said to be a ‘white or yellowish’ area around each eye; but this area, though almost always emphasized in text-book accounts of the animal, is not invariably present.”

To describe this spot as ‘around the eye’ is misleading. In some individuals the very slightly differentiated upper eyelashes certainly are light in colour, but it is only to this extent that the spot may be said to surround the eye. It is, as Bennett describes it, immediately below the inner angle. It is, moreover, present in all the platypus I have seen, including specimens from Queensland and Tasmania in the Australian Museum collections. That it is not invariably present is indicated by Bennett’s observation of an individual without it. Home (1802, p. 70) also records its absence in a male which he examined; he judged from its presence in the female that it was a character for the distinction of the sexes. This is not so, since it is commonly present in males. In dried skins, if the head be not fully filled out, it sometimes becomes involved in the facial furrow, and thus escapes notice; in spirit specimens, as well as in those wet with water, it is often curiously inconspicuous. Thus, out of ten photographs of the one animal illustrating the articles of Hornaday and Joseph (1922) which show the eye, only two (on pages 108 and 109) show the spot clearly. In one or two of the others it can just be made out, but in most it is not visible. Yet it is ordinarily a conspicuous mark, whether on dry land or under water, as may be judged from both subjects shown on Plate 6.

The hair of the platypus, as has been mentioned in the first chapter, has a general fore-and-aft direction, and, apart from the different kinds of hair described above, the only differentiation is to be found in the region of the facial furrow. Here the hair surrounding the eye is slightly modified to form eyelashes of a rudimentary nature, and the aural orifice is lined with short fine hairs, which help to prevent water and particles of soil from gaining admittance. There are no specialized sensory hairs in any part.

The muzzle, which shows some resemblance to a duck’s bill in the dry condition, is very different in the living animal. The naked skin is thick, but soft, moist, and flexible, very unlike the horny beak of a bird. On the upper surface it is slate-coloured; on the under, of a yellowish flesh-colour, often broadly mottled with greenish slate. From the base of each mandible a cuticular flap projects backwards over the fur of forehead and throat. The dorsal flap is longest in the middle line of the head, varying from 17 to 20 mm. in length, and is shorter at each side. The ventral flap is wider at its base than the dorsal, and has a shallow emargination in the middle of its posterior border. Although described separately as dorsal and ventral flaps, these really form round the base of the muzzle one continuous collar, which is only partially divided into dorsal and ventral portions by deep dorso-lateral emarginations. The nostrils open upon the upper mandible at about a third of its length from the anterior end. They are oval apertures with a slight rim-like border, set close together at each side of the middle line. Their anterior borders lie very close to each other, but they diverge obliquely behind. The dorsal portion of the muzzle measures, in an individual of average size, 60 mm. long by 50 mm. wide; it considerably overlaps the ventral portion, which in the same individual measures 42 mm. by 38 mm. (see Plate 8).

The muzzle, with its flaps, is a highly specialized sense-organ. The whole of its exposed surface, both above and below, is pitted with minute pores, which extend on to the cuticular flaps and mark the sites of the highly specialized touch-corpuscles. When under water, the animal depends principally on its delicate sense of touch for finding its way about, and it is fairly certain that the same condition obtains in the burrow. Even when in the open air, it probably depends largely upon the muzzle, since its eyes are so placed that it cannot easily see objects straight in front of it on the ground. The anterior border of the upper mandible is, from its position, the part most brought into use for testing objects, and would seem to be especially sensitive, for the platypus strongly resents its being touched, notwithstanding that it is used for shovelling away loose earth and for upturning river shingle. But the general distribution of touch-corpuscles over the whole of the naked area indicates that all parts are sensitive; and their continuation on to the flaps carries a sure implication that these, too, subserve a sensory function. Many dangers threaten an animal nosing about blindly under water; and it seems probable that the extension of the tactile area in this way is a provision against entering crevices and crannies in which it might be caught. It is well known that it can squeeze through very narrow spaces, and it is possible that the flaps are used as a gauge by means of which it can tell whether it is safe to go on, or wiser to withdraw. Whether this be so or not, the flaps are assuredly a part of the great tactile organ, and not a mechanical shield. In some of the earlier figures, drawn from dried skins, these flaps are shown standing up at right angles from the surface of the head; in the living animal they are always laid back upon the fur, nor does it seem able to raise and depress them to any appreciable extent.

Note impressions in membrane caused by coming into contact with claw tips.

(From fresh carcass)

Plate 9]

The eye and ear are peculiarly arranged. In the half-grown young, running across the front of the head, just under the border of the dorsal flap, there is a groove which on each side turns backwards over the area occupied by the eye and ear (see Plate 12). In the adult the transverse portion of this groove has disappeared, but the lateral portions remain as the facial furrows, in which the eye and ear are situated. The eye, which has suffered most at the hands of artists and taxidermists, is placed at the anterior end of the groove, very close to the dorsal flap, by which it would be partly hidden were not the flap emarginated a little at each side. It is rather small, but exceedingly bright and beady, and has a dark brown iris almost indistinguishable from the pupil. Because of its position it can see only upwards and outwards, and its sole function would appear to be that of detecting moving objects when the beast is at the surface of the water or on the bank. In illustrations the eye is usually placed in the middle portion of the furrow, that is to say, between its true position and that of the ear. Even Gould’s plate exhibits this error. Moreover, the eye is generally depicted too large, and often with a light iris. The plates of Peron and Lesuer (1807) and of Lesson (1839) show a yellow iris, and Waterhouse (1846) in his black-and-white figure shows the iris white. A light iris has been given to many of the specimens mounted in museums, and in these, too, the eye is usually wrongly placed. In life the upper and lower eyelids are not well marked off from the borders of the furrow, but may be distinguished by a slight differentiation of the hair on their margins to form eyelashes. There is a nictitating membrane capable of covering the whole cornea, but I have never seen this employed by the living animal.

The portion of the furrow which contains the eye is partially separated from the auricular part by a fold of skin running obliquely upwards and backwards from the lower border. There is no auricle (external ear). The aural opening is in the form of a deep pit, occupying most of the posterior half of the furrow. The margin is lined inside with short, soft hairs, which prevent the entry of foreign bodies. The opening can be dilated and contracted at the will of the animal, and is in a constant state of motion when it is alarmed or excited. Under water, or while burrowing, the whole furrow is closed by the apposition of its upper and lower margins, and remains so until the head once more emerges. The dorsal position of the eyes, in conjunction with the bulging of the cheeks (due partly to the grit in the pouches) give the sides of the head a heavy-jowled appearance.

The head is joined to the trunk by means of a short and not very well-defined neck. The shape of the trunk varies according to the degree to which the animal is extended. When it is fully stretched in walking, the body appears oblong, and twice as long as it is wide. When squatting, the trunk appears both broader and higher in the posterior region.

The limbs are approximately equal in length, and are highly specialized. The metacarpal region of the fore-paw is covered with hair dorsally; the digits are naked, and are united by a black web, which is extended beyond the tips of the claws for a distance of 15 mm. (in spirit specimens), the extension being supported upon leathery thickenings which take origin from the under surface of the ungual phalanges. Each of the three middle digits has two of these thickenings, arranged symmetrically, but the two outer digits have only one each, placed towards the lateral margin of the paws. The claws are short, straight, and compressed. The palm is black and naked, finely wrinkled, but without any pads such as usually occur on mammalian feet. The fore-paw is the chief swimming-organ, its web being capable of considerable extension in the living creature. On land, that portion which extends beyond the finger-tips is folded under the palm, so that the stout claws may be used for walking and burrowing. The adaptation to two such totally diverse functions is very extraordinary. According to Wood Jones (1923, p. 48) the digital formula is 4 3 2 5 1; but the three middle digits are practically equal in length. In mounted specimens, and in illustrations, the web is always shown in the extended condition, but the animal when on land always has the web tucked under its palms. It is, moreover, never flat, as usually shown, but is always arched, with a dorsal convexity, even when extended.

A somewhat remarkable transformation of the fore-claws is essential before a young platypus can fend for itself. In the nestling stage, the slender claws curve downwards and are grooved beneath. The reason for this curvature is, apparently, to give the nestlings a firm grip of the mother’s abdominal fur when vigorously nuzzling to induce a free flow of milk (see Plate 10). As the nestling grows, the claws gradually become straighter and broader, and instead of remaining grooved, the nails become slightly convex below. By this time the paw is adequately webbed for swimming, and consequently the young one is free to forage alone (see Plate 9).

With each vigorous sweep of the paw when swimming, there is necessarily a severe pressure of the claws against the delicate webbing, and if the claws were not broad and regularly rounded off beneath they would undoubtedly puncture the swimming membrane. The same thing might happen during the toilet process. On examining living adult specimens I have found that, not only is the under surface of the claws convex, but the tips are slightly tilted and there is a considerable amount of resiliency in the nails. Yet, notwithstanding all this, distinct impressions of the tips may be clearly seen in the webbing (see Plate 9). It will thus be seen that although the platypus is a burrowing mammal, the nails are not designed entirely for that particular purpose. This supports my opinion that burrowing is normally attempted only in soil where the sensitivity-lipped bill can also be used.

The hind foot is less remarkable. On the upper side it is covered with hair almost to the ends of the digits, which are webbed. The webbing does not extend beyond the bases of the claws, except for a peculiar narrow prolongation on the inner margin, which lies just within the first digit, and looks like the shadow of its claw. The claws are laterally compressed, and strongly curved outwards and backwards. The digital formula, according to Wood Jones, is 4 5 3 2 1. This foot is scarcely used at all in swimming, except to help tread water, and to aid the tail in steering. On land, the main thrust is due to the feet, but the paws pull with a fair degree of strength. The sole, like the palm, is black, wrinkled, and naked, except for a fringe of hair along its inner border (see Plate 11). In the male a horn-coloured spur is set upon the heel, with a fleshy collar about its base; this spur is movable, and is directed backwards and inwards. In Bennett’s figure (1860, Pl. III), as well as in a number of others contained in authoritative zoological works, the spur is shown on the outside of the foot. This may have been due to a laudable desire to get the spur in at all costs, but it is apt to disconcert the seeker after precise knowledge. In the female, a depressed socket lined with wrinkled skin occupies a position corresponding to that of the spur in the male. The spur is developed in the young of both sexes; in the male it grows normally, but in the female it gradually disappears.

The tail is broad and flat, with the under surface usually a little concave. It is about a third longer than it is wide, with sides slightly converging as it passes backwards, and with broadly rounded end. The hair of its upper surface is exceedingly coarse and harsh; that of the under surface, when not entirely worn off, is softer and lighter in colour. It is a powerful and muscular organ, and an efficient aid in diving, as well as a somewhat less efficient rudder. In nursing females the hair is usually found to be worn off the upper surface. This is caused principally by pushing the pugs back into position in the burrow. Against this view, Wood Jones (1923, p. 48) writes:--

“On general lines, the form of the tail resembles that seen in the Beaver; and this form is, in both animals, an adaptation to surface swimming and rapid diving. It has nothing whatever to do (either in the Platypus or the Beaver) with any supposed habit of puddling clay or flattening down the floor of its burrow or nesting-chamber. When Beavers are alarmed they suddenly smack the water with their flat tails and dive beneath the surface. The loud sound made by the smack of the diving Beaver acts as a warning note to other Beavers in the neighbourhood, and it is probable that the same warning note is produced by the Platypus. The animal has several times been described as making a sound as it dives.”

Note young one clinging to fur and supported by the mother’s tail.

Plate 10]

Note extreme looseness of skin, and tail worn bare with pugging.

Plate 10]

Without supporting evidence, the categorical statement that the tail of the platypus has nothing whatever to do with any supposed habit of puddling clay is not convincing, and I prefer to rely on my own field observations. I must disagree also as to the warning signals. These are common enough among gregarious animals, and the beaver is a gregarious animal. The platypus is not gregarious, but almost solitary, and therefore has no one to warn. Wood Jones writes, it is true, of ‘a considerable colony,’ but I have had no experience of colonies of platypus. The rare occasions when I have found two in company have always caused me surprise. I see no justification, therefore, for arguing by analogy from the herd habits of the beaver to the semi-solitary behaviour of the platypus. When surprised, and beating a hasty retreat, the animal certainly makes a noise in diving; but this has no significance, as I shall explain later on.

The only sure external mark of distinction between the sexes is the spur. Full-grown males are considerably larger than full-grown females; but the immature or young male may be smaller than the female. Ten males taken by me during the spring over a period of several years measured (mm.):--600, 529, 535, 538, 481, 533, 485, 475, 540, 510, averaging 522 mm. Nine females measured (mm.):--406, 402, 414, 460, 475, 433, 451, 421, 407, averaging 430 mm.

Measurements of spirit specimens and skins in the Australian Museum are:--

MALE. FEMALE. Spirit Specimens. 445 mm. 398 mm. 405 mm. 392 mm. 455 mm. --

Skins 561 mm. 483 mm. 560 mm. 478 mm. 510 mm. -- 537 mm. --

Average of 7 = 496 mm. Average of 4 = 413 mm.

Bennett (1860, p. 102) gives the average measurements of freshly-killed males as from 19 to 20 inches (483 mm. to 508 mm.); and of females as from 18 to 19 inches (457 mm. to 483 mm.).

We may next consider the nature and heat of the blood. In amphibia, reptiles, and birds, the red blood-corpuscles are oval, nucleated discs. In mammals they are non-nucleated, and in all save the camels are circular. The platypus has typical mammalian corpuscles, of about the same size as those of man. Cold-blooded animals (amphibia and reptiles) have no heat-regulating apparatus, and their temperature tends to rise and fall in accordance with that of the surrounding medium, whether it be earth, air, or water. In mammals and birds, on the other hand, the heat-regulating mechanism tends to keep the temperature constant within a degree or two, regardless of the external medium. This difference in blood-heat causes striking differences in habit. The cold-blooded animal is forced to hibernate during the winter, at least in places where there is a considerable difference between the mean winter and summer temperatures; the depression of temperature renders it inactive. The warm-blooded animal, on the other hand, eats more food, and moves about actively in order to produce the heat necessary to keep up its body temperature.

It has been claimed that the monotremes exhibit an intermediate condition, and are not completely warm-blooded. On this point, however, I am in full agreement with Wood Jones (1923, pp. 38-39), and quote his discussion of the matter:--

“In the same way we must admit that the body temperature of the Monotreme is unusually low; but that is not to agree that they are akin to the Reptiles in failing to maintain their body temperatures within certain fairly definite limits.

“The temperatures of seven females of the Platypus were taken by Mr. Burrell. These females were removed from their nesting chambers, and the observations were made in September. The temperature of these animals ranged between 30°C. and 33°C., and the average of all the observations was 32.2°C.

“Of Echidna there are many temperature records, since it is an animal which is easily kept and examined in captivity. Miklouho-Maklay, in 1879, examined a series of ‘porcupines,’ and concluded that their temperature ranged between such low figures as from 26.95°C. and 28.3°C. In 1886, R. von Lendenfeld, as the result of a series of observations, concluded that the body temperature was higher, but more variable, and they give the extremes as 28°C. and 35°C. Semon, in 1894, gave 26.5°C. to 34°C. as the range for Echidna. Sutherland, in 1897, found it to be as wide as from 22°C. to 36°C. Dr. C. J. Martin re-investigated the question in 1902, and during the last few years Dr. Wardlaw has made innumerable observations, and, thanks to his work, we may say that the peculiarities of the body temperature of the Monotremes are now well known.

“The temperature of the higher Mammals varies within fairly wide limits, and in the different species that have been examined it ranges from about 36°C. upwards for a few degrees. It is therefore obvious that both Ornithorhynchus, with its average of 32.2°C., and Echidna, with its average of 31.1°C., are creatures of relatively low temperature; but the difference between the Monotreme temperature and that of other Mammals is not nearly so great as it is often asserted to be. It must also be remembered that our knowledge of the temperatures of some of the lower Monodelphia is scanty, and it is possible that Echidna and Ornithorhynchus do not stand very far apart from some of the more sluggish and least advanced of the higher Mammals in the matter of their bodily heat. Again, the fact that the temperature of the Monotremes varies at different times of the day does not confer on them the distinction that some writers have imagined. Dr. Wardlaw determined that the morning temperature was always lower than the afternoon temperature; but the same is true of the higher Mammals and of man. Semon noted this variation in the temperature, but confessed that ‘a relation between these changes and the changing temperature of the outer air could, however, not be proved.’ That is to say, although the temperature of Echidna is variable, its rise and fall does not correspond with the rise and fall of the temperature of its surroundings, as is the case with the lower Vertebrates. There is, nevertheless, a time when the temperature of Echidna does tend to follow the temperature of the outside air, and when the Monotreme can be said to behave somewhat like a ‘cold-blooded’ or poikilothermic animal. This is during that period of the year when the animal undergoes a partial hibernation or aestivation. In the summer Dr. Wardlaw’s animals averaged 30°C. in the morning and 32.6°C. in the afternoon; but in the winter the morning temperature was 29.7°C. and the afternoon was 32.3°C.; but this fall in winter temperature is found in all hibernating or partially hibernating animals; and it can only be said that the Monotremes are animals having a rather low body temperature, but, nevertheless, being truly homoeothermic (or ‘warm-blooded’) within certain limits of temperature, and in the non-hibernating period. They have a typically good mammalian heat-regulating mechanism, effective between 27.6°C. and 32.6°C.; and it is only when the temperature is raised or lowered beyond these limits that the regulation tends to break down, and they behave as poikilothermic animals.”

Note tip of spur projecting behind and above ankle.

(From fresh carcass)

Plate 11]

Note base of spur unsheathed; this readily occurs after death, but seldom during life. Compare with Plate 15 (1).

(From fresh carcass)

Plate 11]

Following is a table of cloacal and atmospheric temperatures (Fahr.) observed by me during five years of field work.

MALE PLATYPUS.

Cloacal Atmospheric temp. shade temp. 8/10/23 84° 53° 18/9/25 82° 63° 19/9/25 87° 79°

FEMALE PLATYPUS.

20/9/20 88° 70° 23/9/21 87° 82° 5/10/21 88° 68° 8/10/23 84° 53° 15/9/24 84° -- 7/10/24 82° -- 8/10/24 90° 46° 14/3/25* 90° -- 24/8/25 86° 64° 24/8/25 92° 64° 28/8/25 94° -- 3/9/25 82° 70° 10/9/25 89° 74° 18/9/25 82° 63° 26/9/25 86° 66°

March may be reckoned as midway between rutting periods.

* With this exception, all the females were brooders taken from nests.

Two temperature readings of wild echidna specimens, made directly after collection in mid-September 1924 and 1925, were found by me to be respectively:--

1. Cloaca, 90° Fahr. Pouch, containing young, 84° Fahr. 2. Cloaca, 79° Fahr. Pouch, containing young, 82° Fahr.

I did not record the atmospheric temperature when the 1924 specimen was taken; but I noted that it was an exceptionally cold day. When the second was taken, it was 70°.

By attaching an adult platypus to a spring scale I found that it could pull steadily (on level ground) six pounds, and up to twelve by jerking. The bottom jaw, when open, can pull seven pounds in the gradual closing.

Characteristics common to the platypus, to reptiles, and to birds are the single aperture or vent into which the intestinal, urinary, and reproductive systems open, and the laying of eggs. The “scientific” name (Ornithorhynchus) together with its commonly-accepted early vernacular name of “duckbill,” its webbed feet, and the discovery of its eggs have contributed to the existing impression, except among zoologists, that the platypus is essentially bird-like; but, as a matter of fact, while it is clearly a mammal, its remote origin has been proved to be reptilian. Apart from this scientific conclusion I would like to outline for general readers some external characteristics of the platypus which I consider to be possessed also by certain reptiles.

The study of an animal in its adult stage is apt to lead one to look for its relations in more modern forms, whereas in its embryo and nestling stage it is more likely to exhibit the characteristics of its forbears. By looking backward we may, therefore, occasionally detect a trait connecting the platypus with much earlier forms in the evolutionary cycle--a trait which in the mature animal would easily escape notice, even if it had not entirely disappeared.

To begin with the egg--quite apart from the leathery texture of the capsule, the fact that the foetus has developed to a considerable extent before deposition is positively reptilian in character.

The tortoise-like overturning of a platypus, though inconspicuous in the adult, is, nevertheless, deliberately and systematically accomplished by the unfurred nestling, and this at a stage when their limbs are of little assistance. Like a tortoise, a young platypus, when floundering on its back, pivots its snout firmly in the ground, then arches its neck, throat uppermost, until, by such strenuous leverage, the shoulders are sufficiently raised to allow the wriggler to over-balance on to its abdomen.

Another reptilian trait peculiar to the young of platypus is their power of endurance when wholly submerged in water, and, strange though it may appear, the younger the subject the greater that power. This is described more fully in the chapter on the breeding-burrow.

The male platypus and echidna are the only known mammals with poison glands, and this forms another link with the reptiles.

From a dorsal aspect, the fur-tracts of Ornithorhynchus trend uniformly towards the tail, in a manner similar to that of the scale pattern conspicuous in snakes, etc. It is true that slight semi-whorls or waves of fur occur ventrally, and about the cheek-pouches, but even this is not entirely wanting in the scale pattern of reptiles.

Spurs, or “hooks” as I prefer to call them here, are to be found on the fore-flippers of the male Green Turtle; but whether they are used as weapons of defence I cannot say. My opinion is that, like those of a platypus, defence is one of their purposes. From personal observation of both creatures, however, I know that their hooks are used for gripping during copulation. Incidentally it may be remarked that both of these creatures perform this function in water. It is of prolonged duration in both cases; therefore an untiring grip is essential.

The casual gait of a platypus is somewhat akin to that of a Stump-tailed Lizard, while the chubby tails which both animals possess are sufficiently near in design not to be overlooked in this matter.

The small and beady bright eyes of Ornithorhynchus, also their position and the direction of their vision, are similar to those of certain reptiles, as is also the dorsal position of the rigid nostrils.

Although represented in swimming birds, the webbing of the feet of the platypus is found also in reptilian quadrupeds.

The contorting ability of an adult platypus is quite remarkable. It can extend its length six inches without raising its abdomen from the ground. When it is in a crouching attitude, with the back conspicuously humped, it is impossible to see daylight below, and the contour of the whole body resembles that of a squatting echidna. When lying fully extended on its back, the platypus can, by placing the lower portion of its bill on its breast, and without raising its head to any appreciable extent, double itself ventrally until its head passes its tail, and that pliable member is itself doubled until the creature becomes normally righted on all fours, dragging its tail behind it. This act it can accomplish in a tunnel equal in circumference to the performer so doubled. When balled-up, as in the sleeping position, the tip of its tail will reach over the head to the scapular region. In the reversed position the tail-tip reaches to the gullet, above the back. In turning sideways, with abdomen on the ground the while, tail and bill just make contact. The head can be turned sideways at a right angle to the body, and the tail can be moved either to form a right angle with the rump or to lie comfortably along the contour of the back, except at the base, where one can just insert the tip of an index finger. These few items are additional to the animal’s capacity for muscular expansion and oscillating limb-functions, and they give some notion of what the platypus is capable of when hard pressed or in a tight corner.

Finally, the platypus, like the reptiles, has no external ears and is flealess, though ticks are common to both. One is known by the company one keeps.

Note serrated edge of bottom lip.

Plate 12]

Note swimming membrane extending beyond claw tips of fore-paw; grip of hind foot and tick on thigh; also that the eye is closed and the ear-hole open.

Plate 12]