Part 27

Omomys, Leidy, Journ. Acad. Nat. Sci. Philad., vii., p. 408 (1869).

This genus was established for the first Mammalian fossil--a lower jaw--described from the Bridger-beds as O. CARTERI. The posterior lower molar has cusps in opposing pairs; pre-molars, three in number, the two anterior one-cusped, the posterior two-cusped. The chin was longer and less rounded than in Anaptomorphus.

GENUS ANAPTOMORPHUS.

Anaptomorphus, Cope, Proc. Amer. Phil. Soc., 1872, p. 554; id., Rep. U. S. Geol. Surv., iii., p. 245, pl. xxiv. e, fig. 1; xxv., fig. 10.

This genus was founded by Cope on an almost entire cranium discovered in the Bridger (Eocene) beds of the upper Valley of Green river, and on other remains from what is known as the Wasatch formation of the Big-Horn Basin in Wyoming Territory, in North America. The external upper incisor is small and set close to the small canine; the pre-molars have each a large external and a smaller internal cusp; the true molars are wide and have one internal and two external cusps. In the lower jaw the two anterior molars are four-cusped, with a transverse ridge between the anterior pair, and an oblique ridge between the hind inner, and the front outer, cusp; the posterior is three-cusped and has a heel. The orbits are enclosed, as in typical Lemurs. Not less typical characters are the position of the lachrymal foramen, external to the orbit, and the unossified halves of the lower jaw. "Its dental formula (I2/2, {118}C1/1, P2/2, M3/3) agrees only with the Indrisinæ. But no known Lemuridæ possess anterior lobes and cusps on all the pre-molars, so that in this respect, as in the number of its teeth, this genus resembles the higher Monkeys, the Simiidæ and Hominidæ, more than any existing member of the family.... It has ... a number of resemblances to Tarsius, which is, perhaps, its nearest ally among the Lemurs, although that genus has three pre-molars.... There is no doubt but that the genus Anaptomorphus is the most Simian Lemur yet discovered...." (Cope.)

The species included in this genus are A. ÆMULUS (Cope), which did not exceed the size of a Marmoset or a Red Squirrel, and had short erect incisors; A. HOMUNCULUS (Cope), a species founded on a cranium without a lower jaw, with the orbits not so large as in Tarsius, and the skull wide behind the eyes. "The A. homunculus was nocturnal in its habits," according to Professor Cope, "and its food was like that of the smaller Lemurs of Madagascar and the Malayan islands. Its size is a little less than that of the Tarsius tarsius."

Two other insufficiently characterised genera, both considered to be primitive Lemuroids, are Plesiadapis, Gervais, containing the species P. REMENSIS, P. GERVAISI, P. TOURNESARTI, and P. DAUBREI, from the Lower Eocene strata of Rheims, which have five-cusped lower molars, and enlarged upper and lower incisors; and Protoadapis, Lemoine, with one or two high front cusps, and a low heel to its three pre-molars; the anterior molars with two pairs of opposite cusps, the posterior molar with a fifth cusp on the hind border. P. CRASSICUSPIDENS, Lemoine, and P. RECTICUSPIDENS, Lemoine, are its two species.

{119}FAMILY ADAPIDÆ.

The different species associated together under this family are abundantly known from the Upper Eocene of France, England, and North America. They are remarkable in having an extra pre-molar in both jaws, the dental formula being I2/2, C1/1, P4/4, M3/3.

GENUS ADAPIS.

Adapis, Cuvier, Ossem. Foss. (2) iii., p. 265 (1822); Flower, Ann. and Mag. N. H., xvii., (1876), p. 323.

Palæolemur, Delfort., Act. de la Soc. Linn. Bord., xxix., pp. 87-95, pl. 5 (1873); id. C. R., lxxvii., p. 64 (1873).

Aphelotherium, Gervais, Zool. et Pal. Franç. (1), ii., Exp. 34 (1848-52).

Cænopithecus, Rütim, Denksch. Schw. Ges. Nat., xix., p. 88 (1862).

Notharctus, Leidy, Geol. Surv. Mont., p. 364 (1871).

? Thinolestes, Marsh, Am. Jour. Sci., 1872 (2), p. 205.

? Telmalestes, Marsh, op. cit., p. 206.

"The general form of the cranium," to quote Sir W. Flower, "the large size and anterior direction of the orbits, the small and narrow muzzle ... show its affinity to the Lemurine animals, and especially to the African forms. The whole skull, however, is more depressed than in the slow Lemurs and Galagos; the orbits are smaller, the brain cavity relatively smaller and more constricted behind the orbits, and the muscular ridges more developed."... The lower jaw is deep and stout. The posterior upper pre-molar is very similar to a true molar. "The upper molar teeth are nearly equal in size, and have nearly square crowns, with four distinct cusps, one at each angle, rather obliquely placed"; the hind inner cusp {120}of the posterior molar inconspicuous. The lower molars have two pairs of obliquely placed cusps, connected by transverse ridges, anterior and posterior, with an oblique ridge running forwards and inwards from the outer hind cusp. The hindmost lower pre-molar has an internal cusp; the lower incisors have upright spatulate crowns like those of true Apes.

Several species of this genus have been described. ADAPIS PARISIENSIS (with the synonyms of Aphelotherium duvernoyi, Gervais, and Palæolemur betillei, Delfortrie) is one of the best known, and its remains have been found in Upper Eocene strata at Egerkingen, in Switzerland, at Sainte Néboule de Béduer, and in the Paris Gypsum, in France, as well as in England. It "more nearly resembles the Indo-African Lemurs, and not those of the island of Madagascar, or of the extreme east, having no near relationship with the Tarsius, the Aye-Aye, or the Indris, and not much with the true Lemurs." (Flower.) From the Eocene of Switzerland comes A. LEMUROIDES. ADAPIS MAGNA (Filhol) is larger than the preceding species, has a larger face, and a greater constriction between the cerebral and facial regions of the skull. It has been found in the phosphatic deposits at Raynal, in France. ADAPIS ANGUSTIDENS (Filhol), from the Quercy Phosphates of France, is distinguished by the structure of its molars, and by the great size of its two anterior pre-molars. A. TENEBROSUS (Leidy) has a large lower canine. A. MINOR (Filhol) is an additional species.

GENUS TOMITHERIUM.

Tomitherium, Cope, Vert. Bridg. Eoc. Wyom., p. 2, 1872.

Limnotherium, Marsh, Am. Journ. Sci., 1871, ii., p. 43 (in part).

This genus, which is allied to Adapis, is characterised by {121}having its lower incisors with cutting edges; the first and second lower pre-molars with one root; the third with one cusp and a posterior heel, and the fourth an interior lateral cusp in addition. The lower true molars have two anterior cusps (the inner being double) and two posterior. The thigh is long and the knee free from the body as in the Anthropoidea, the hand capable of turning freely upwards at the wrist; the hind-limbs longer than the fore-, and "the details of the lower jaw, which is co-ossified in the centre, and teeth similar to that of the lower Monkeys." The remains of the only known species, T. ROSTRATUM (Cope), which was about the size of the Capuchin Monkey (Cebus capucinus) of Brazil, were found in the Bridger (Eocene) beds in an isolated spot on Blacks' fork, Wyoming.

GENUS MENOTHERIUM.

Menotherium, Cope, Bull. U. S. Geol. Surv. Territ., 1874, i., p. 22.

Laopithecus, Marsh, Am. Journ. Sei., 1875, i., p. 240.

This genus was established on an under jaw from the Lower Miocene White-river beds of Nebraska. Its molars are successively larger from anterior to posterior; the two pairs of cusps are obliquely opposite, the hinder pair longer than the front pair, and presenting a strong cingulum. Its discovery was the first indication of Lemurs in the Miocene of the United States. M. ROBUSTUM, Marsh, was as large as a Coati; and M. LEMURINUM (Cope) about the size of a domestic Cat.

GENUS PELYCODUS.