Section 1. Sciuromorpha.

The Anomaluri are separated by Thomas and others from this section as an equal section, while by Tullberg they are grouped with Pedetes.

FAM. 1. ANOMALURIDAE.--The genus Anomalurus suggests at first sight the Flying Squirrels of Asia, Pteromys. It is, however, an entirely African genus, and is to be distinguished from the Asiatic Rodents by a series of scales at the root of the tail, imbricated, keeled, and forming possibly a "climbing organ." This character serves also to distinguish the present genus from Sciuropterus. The cartilage, moreover, which supports the patagium springs from the elbow. There are four molars in each half of each jaw. The eyes and ears are large. There are five fingers and toes, but the thumb is small, though provided with a nail. The sternum has seven joints, and nine ribs reach it. The clavicle is strong. Huet, who has recently monographed the genus, allows six species. The species vary in size. {463}

Anomalurus peli appears, according to Mr. W. H. Adams, to be a common species on the Gold Coast; it is coloured black and white, but in spite of the warning which this colour should convey, is considered by the perhaps rather omnivorous native as "the greatest delicacy." The animal is nocturnal, but affects only bright moonlight nights. Their "flying" consists of a jump from a high branch to a lower one, after which they reascend the tree to a point of vantage for another jump. They are said to feed upon nuts; but Tullberg only found the remains of leaves in the stomach.

Idiurus is a lately-described genus allied to Anomalurus. There are at any rate two species, I. zenkeri and I. macrotis. The thumb is more reduced than in Anomalurus, and the fibula, contrary to what is found in that genus and in most Sciuromorphs, is fused with the tibia below.

A third genus, very recently described and allied to both the foregoing, is Aethurus. It is a native of the French Congo, and differs by the absence of flying membranes. It has, however, the pad of large scales. There is but one species, A. glirinus. It has a black bushy tail. The postorbital processes of the frontals are totally wanting--there are not even the traces to be seen in Anomalurus. The thumb has vanished. If we are to compare Anomalurus with the Squirrels then, thinks Mr. de Winton, the present genus is probably diurnal by reason of the want of flying membranes.

FAM. 2. SCIURIDAE.--The Squirrels, genus Sciurus, are world-wide in range, the Australian region and the island of Madagascar being alone excepted.

The eyes and the ears are large; the tail is of course long and bushy. The fore-feet have an inconspicuous thumb; the hind-feet have four toes. The soles of the fore-feet are naked or furry, those of the hind-feet are hairy. There are twelve or thirteen dorsal vertebrae, and in correspondence seven or six lumbars. The caudal vertebrae may be as many as twenty-five. In the skull the frontals are broad, and there are long {464} postorbital processes. The infra-orbital foramen is, as a rule, not large, but is increased in size in a few forms. The number of separate pieces of bone in the sternum is five. The molars of the upper jaw are five, but the first is very small and soon drops out.

The Squirrels are often rather brilliantly coloured. The Chinese Sc. castaneiventris has grey fur with a rich chestnut-coloured under surface. The Malabar Squirrel, Sc. maximus, as its name implies, a large animal, has a deep reddish or chestnut-coloured fur above, which becomes yellow below. The "Common Squirrel," "the lytill squerell full of besynesse," which is the Squirrel of this country, is brownish red on the upper parts and white below. It ranges from this country as far east as Japan. Like many other Rodents the Squirrel likes animal food and will eat both eggs and young birds. "Camel's hair" brushes are made from this animal. The genus Tamias, almost exclusively North American in range, is included by Dr. Forsyth Major in this genus, which then consists of considerably over one hundred species.

The Ethiopian Ground Squirrels, genus Xerus, have a more elongated skull than Sciurus, and the postorbital processes are shorter. The feet are not hairy.

Nannosciurus forms a perfectly distinct genus of Squirrels. These "Pygmy Squirrels" differ in possessing a very elongated "face" and in the very broad frontal region. The teeth are unlike those of Sciurus in certain features, and have been especially compared by Forsyth Major to those of the Dormice. Four species of this genus are Malayan; one is West African.

The Bornean Rheithrosciurus macrotis is the only species of its genus. The genus may be distinguished by the exceedingly brachyodont molars, this feature being more marked in this genus than in all other Squirrels. It is called the "Groove-toothed Squirrel," from the "seven to ten minute parallel vertical grooves running down the front face of its incisors."

The genus Spermophilus includes a large number (forty or so) of Palaearctic and Nearctic animals known as Sousliks. The ears are small; there are cheek pouches as in Tamias. The general aspect of the animal is like that of a Marmot, and they bridge over the exceedingly narrow gap which separates the Marmots from the true Squirrels. Anatomically the skull is like that of {465} Arctomys; the molars are five in the upper and four in the lower jaw. The caecum is relatively speaking very small; the measurements in a specimen of S. tredecimlineatus, dissected by Dr. Tullberg, were: small intestine, 580 mm.; large intestine, 170 mm.; and caecum, 27 mm. In Tamias also the caecum is not greatly developed. These animals are burrowing in habit.

The Prairie-dogs, genus Cynomys, of which the best-known species is perhaps C. ludovicianus, are very like the Squirrels, but they are not arboreal creatures; they live in burrows on the ground, as their vernacular name denotes. The genus is entirely North American, and four species have been differentiated.

The Prairie-dog or Prairie-marmot is some 10 inches to one foot in length. The tail is no more than 2 inches. The ears are very small; the thumb is fully developed and bears a claw. The measurements of the various sections of the intestine are the following:--Small intestine, 860 mm.; large intestine, 690 mm.; caecum, 75 mm. Thus the caecum is not large comparatively speaking. These animals dig burrows on grassy plains which they share with the Ground Owl (Speotyto cunicularis) and with Rattlesnakes, all three species appearing to live in perfect amity. Probably the Owls use the conveniently-constructed burrows, and the Rattlesnakes come there to look after the young of both.

FIG. 233.--Long-tailed Marmot. Arctomys caudatus. x 1/7.

Closely allied to the last are the Marmots, genus Arctomys. They differ in the rudimentary character of the thumb and in the longer tail. The eyes and ears are small. The distribution of the genus is Nearctic and Palaearctic. There are ten species of {466} the genus. The Alpine Marmot, A. marmotta, is familiar to most persons. The animal lives high up in the Alps, and when danger threatens it gives vent to a shrill whistle. It hibernates in the winter, and as many as ten to fifteen animals may be found closely packed together in a single, carefully-lined burrow.

The only other European species is A. bobac, the Siberian Marmot, which occurs in the extreme east of Europe, and is also Asiatic. There are four North American species, including the Quebec Marmot, A. monax.

FIG. 234.--Flying Squirrel. Pteromys alborufus. x 1/5.

The genus Pteromys (of which the proper name, antedating Pteromys by five years, appears to be Petaurista) is confined to the Oriental region, where there are a dozen species or so. The limbs are united by a parachute extending to the toes, and supported anteriorly by a cartilage attached to the wrists. There are also membranes anteriorly uniting the fore-limbs to the neck, and posteriorly uniting the hind-limbs to the root of the tail and a trifle beyond. The skull and the dental formula are as in Sciurus, but the pattern of the molars, which is much complicated, seems to argue a different mode of nutrition. There are twelve pairs of ribs. The large intestine (in P. petaurista) is very nearly as long as the small, and the caecum is also "colossal"; the measurements in an individual of the species named were: small intestine, 670 mm.; caecum, 320 mm.; large intestine, 650 mm. {467} The caecum is disposed in a spiral. The teats are three pairs, non-inguinal in position.

The size of these squirrels is 16 to 18 inches exclusive of the tail, which is longer. These animals can make an exceedingly long jump with the help of their flying membrane. Nearly eighty yards is the longest distance given for these aerial excursions. It is stated that they are able to steer themselves to some extent while in the air. As appears to be the case with so many Rodents, these animals feed largely upon beetles and other insects, besides bark, nuts, etc.

The allied genus Sciuropterus has a much wider range. It extends into the Palaearctic region and into North America, besides being found in India. There is here no membrane reaching to the tail. The palms and soles are furry. The caecum is very much shorter, and so is the large intestine. The latter, in S. volucella, is not more than one-third of the length of the small intestine. In other features there are no remarkable differences in structure, save that the mammae, always three pairs, may be inguinal.

Of the genus Eupetaurus but a single species is known, which is limited to high altitudes at Gilgit and perhaps in Thibet. Its principal difference from the other genera of Flying Squirrels is that the molars are hypselodont instead of brachyodont. The interfemoral membrane is rudimentary or wanting. The one species is E. cinereus. It is thought to live "on rocks, perhaps among precipices." Dr. Tullberg attributes the hypselodont teeth to the fact that the mosses upon which it is believed to feed may have much sand and earth intermingled, which would naturally lead to a more rapid wearing away of the teeth, and hence a need for a good supply of dental tissue to meet this destruction.

FAM. 3. CASTORIDAE.--This, the third family of the Sciuromorpha, contains but one genus, Castor, the Beaver, with at most two species, one North American, the other European. This large Rodent has small eyes and ears, as befits an aquatic animal, and the tail is exceedingly broad and covered with scales; the transverse processes of the caudal vertebrae, in order better to support the thick tissues lying outside them, are divided in the middle of the series into two. The hind-feet are much larger than the fore-feet, and are more webbed than in any other aquatic Rodent. {468}

In the skull the infraorbital foramen is small as in Squirrels. The postorbital process has practically vanished. The four molars stand out laterally from the jaws. The incisors, as might be surmised from the habits, are particularly strong. The stomach has near the entrance of the oesophagus a glandular patch, which seems to be like that of the Wombat (see p. 144). In both sexes the cloaca is very distinct and comparatively deep.

The two species of the genus are C. canadensis and C. fiber. The latter is of course the European species, which is now found in several of the large rivers of Europe, such as the Danube and the Rhone. But it is everywhere getting scarce, and limited to quite small and isolated colonies.

In this country it is absolutely extinct and has been since before the historic period. There is apparently no documentary evidence of its survival down to this period. But the numerous names of places which are called from this animal illustrate its former prevalence. Examples of such names are Beverley in Yorkshire, and Barbourne or Beaverbourne in Worcestershire. In Wales, however, Beavers seem to have persisted longer. But they were rare in the Principality for a hundred years or so before the Norman Conquest. The king Howel Dda, who died in 948 A.D., fixed the price of a Beaver skin at 120 pence, the skins of Stag, Wolf, and Fox being worth only 8 pence apiece. The Beaver was called by the Welsh "Llost-llyddan," which means "broad-tail." Its existence in the country is handed down in the name of Llyn-ar-afange, which means Beaver lake. The last positive record of the Beaver in Wales seems to be the statement of Giraldus Cambrensis that in 1188 the animal was still to be found in the river Teivy in Cardiganshire. In Scotland the Beaver is said to have continued down to a later date. Ireland it never reached. The remains of this animal by their abundance show the former prevalence of C. fiber in this country. It is known from the fens of Cambridgeshire, and from superficial deposits elsewhere. The Thames formerly had its Beavers, and apparently it was widely spread through the country generally.

The Beaver not only furnishes collars and cuffs for coats; it was used, as every one knows, to provide hats. But the usefulness of the animal by no means ended here in the eyes of our {469} forefathers. The Rev. Edward Topsell observed that "for giving great ease unto the gowt the skinnes of beavers burned with drie oynions" are excellent. Castorein as a drug, if not in actual use, has quite recently been a part of the pharmacopoeia. It is derived from the anal glands common to this and other Rodents, and indeed many other mammals.

A large extinct form of Beaver is Trogontherium, found in the "Forest-bed" of Cromer. The skull is about one-fourth longer than that of Castor. It has a less inflated bulla, and slightly more pronounced postorbital processes than Castor. The third molar (fourth grinding tooth) is relatively larger than in Castor, and has a rather more folded crown. The foramen magnum is more triangular.

FAM. 4. HAPLODONTIDAE.--A separate family seems to be required for the genus Haplodon, whose characters will therefore be merged with those of its family. It is to be distinguished from most other Squirrel-like creatures by the fact that there is no postorbital process to the frontal. The molar teeth are five in the upper and four in the lower jaw. The Sewellel, H. rufus, like the other species of the genus (H. major), is found in North America west of the Rocky Mountains. It has the habit of the Prairie-marmot, and has a short tail, only moderately long ears, and five-toed feet. Tullberg is of opinion that this animal nearly represents the ancestral form of the Squirrel tribe.