AND AVES OF NORTH AMERICA 



83 



APPENDIX TO THE CROCODILIA. 



PEROSUCHUS, Cope. 

 Proo. Acad. N. Soi., Phila., 1868, p. 208. 



Characters. — Toes 5 — 4, with claws two-three. No osseous nasal septum or bony eyelid. Belly protected by 

 series of osseous plates, as well as the back. 



All the genera of Crocodiles hitherto known as living, are characterized by the possession of three claws on 

 the fore-foot. The present therefore offers a remarkable exception. The free lingers and half webbed toes, and the 

 bony abdominal buckler, together with the cartilaginous nasal septum, are points of strong resemblance to Jacare 

 (Gray including Oaeman Gray) but it differs from these creatures in the lack of bony orbit. In specific characters it 

 differs from those of this genus which it most resembles — as J. nigra, in the absence of a transverse bony ridge 

 between the orbits. Another feature of importance is the relation of the canine teeth of the lower jaw to the upper. 

 On one side this tooth is received into a notch as in Crocodiles, on the others, il, enters a. pit of the maxillary bone, 

 within the border of the same as in Alligators ! This remarkable combination may be abnormal even in this species, 

 but, this cannot, be now ascertained, as it, rests at the present, time on a single specimen only. As its affinities are 

 rather more AAligatorial, I am disposed to anticipate that the dental arrangement of the latter animals will be most 

 oommon. 



Fig. 21. 



Fijr. 33. 



g 



CSf 



Fig. 22 



.' c *rfir- 



Fig. 24. 



PEROSUCHUS FUSCUS, Cope. 



Char, tpeciflcus. —Nuchal plates in a oross row of six ; cervioals in four cross-rows, all of four plates except the 

 last, of two. Dorsal plates in six- — in a few eight in each transverse row. No posterior crest on arm or leg. Tail 

 short with remarkably low crest,. Muz«sle broad Mat, without any ridges; its width at the eighth tooth entering 1.4 



in length from cud muzzle to anterior margin of orbit. 



Description. The specimen in the Museum of the Academy is young, measuring only 2 feet 5 inches in length. 

 Of this the skull measures to the margin of the supra-occipital 2 in. 10.5 lilies ; and the tail to the vent 13 in. 7 lin. 

 From groin to heel 3 in. 2.5 lin., and the hind foot 3 in. 7.5 I'm. The muzzle is a, broad ovale, the sides rather more. 

 convergent anteriorly than in the Alligator mmissippiensis. There is a thickening in front of each orbit, and 



