ZEUGLODONT AND OF LEATHERY TURTLE. 313 



surface of the centi'uui is nearly flat, and between its lateral 

 edge and the broken base of the transverse process is a well- 

 niai'ked concavity. The ventral surface has a strong prominence 

 in the middle line, deepening towards its posterior border. 

 In the middle line on the dorsal surface, on its posterior half, is a 

 deep circular pit — probably the nutritive foramina opened into it. 

 A similar depression has been noticed on the axes of a Cave-Bear 

 and of the Cveodont Apterodon \ probably it is found elsewhere, 

 but it is not seen in two axis vertebrae of Frozeuglodon. Compared 

 with the 'Axis oi Protocetiis as figured by Fraas*, this specimen 

 has a blunter odontoid, the lateral surfaces for the atlas slope 

 more strongly backwards, and the posterior surface is much wider 

 in proportion to its depth. In Protocetus the centrum is about 

 as long and has a similar ventral prominence. In Frozeuglodon "f 

 the whole vertebra is shorter, the ventral ridge is indicated only 

 by a slight posterior prominence, and the surfaces for the atlas 

 do not slope so much backwards. The length of the centrum 

 and the backward slope of the atlantal surface, the width of 

 the posterior surface and the ventral jix'ominence, seem to be 

 primitive characters, approximating to what is seen in the 

 Carnivore-Oreodont group. 



This new Zeuglodont, for which the name Fapjyocetus lugardl 

 is suggested, is especially interesting on account of the Car- 

 nivore-like characters of the teeth, which seem to point to a 

 Creodont-Carnivore ancestry as was suggested by Fraas from his 

 study of the Middle Eocene genus Frotocetus J. Unfortunately 

 in this animal only the upper dentition is known, but pro- 

 bably the lower teeth were not veiy unlike those now described. 

 To this relationship with the Creodonts some objections have 

 recently been raised by Matthew and Gregory §, who point to 

 a number of chai"acters which seem to indicate that the 

 Zeuglodoufcs may have branahed off from the primitive Insecti- 

 A'ora, perhaps from some such form as the Eocene Fantolestes, a 

 type which, at any rate, shows that souie of the early members of 

 the order attained a considerable size and became adapted to 

 an aquatic lifelj. Attention is also drawn to the remarkable 

 superficial similarity in the form of the Zeuglodont skull to 

 those of some of the Centetidte, notably Ilemicentetes. This 

 similarity is also particularly noticeable in the form of the 

 mandible, in which even so small a point as the step-like notch 

 on the ventral border is present, though farther back. In the 

 structure and arrangement of the teeth there seems to be 

 nothing that altogether excludes the possibility of such a 



* Pvaas, " Neue Zeuglodouteii aus dem uiitereii Mitteleocan vom Mokattain bei 

 Cairo," Palaiont. Abliaiidl. E'd. x. (1902-5), p. 211, pi. ii. figs. 2-5. 



t Andrews, Catal. Tertiary Vertebrata of the Fayum (1906), p. 2oi, text -fig-. 83 

 B-D. 



X PaLuont. Abliandl. n. s. Bd. yi. (1904), p. 199. 



§ "The Orders of Mammals," Bull. Amer. Mus. Nat. Hist. vol. xxvii. (1910), 

 p. 414. 



II Memoirs of the Amer. Mus. Nat. Hist. vol. ix. (1909), p. 52.3. 



