P.N.E.Z.C. 



104 FOWLER — PEROSUCHUS COPE [^Vof. V 



appears to me doubtful whether the absence of the claw in the third 

 finger will prove a constant character." ^ With reference to the 

 absence of a transverse bony ridge between the orbits in Pero- 

 suchus, Cope makes a comparison of his type with Caiman niger 

 Spix, but not with Caiman sderops (Schneider). Yet with the 

 latter species I feel certain it is identical. In every other respect, 

 save the irregular and variable disposition of the fourth enlarged 

 mandibular teeth, it agrees. On the left side this tooth fits into 

 a deep notch in the upper jaw; on the right side the tooth fits 

 into a socket, and the upper surface has an aperture through which 

 the tip of the tooth may be seen when the jaws are closed completely. 

 Thus, speaking broadly, on one side — probably due to a pathologi- 

 cal condition — a notch may be seen, while on the other there is the 

 typical Caiman socket. A comparison of the specific characters 

 with those of Caiman sderops leaves nothing of importance which 

 could not be included in the limits of the latter wide-ranging form. 

 As the figures of his type, given by Cope, are quite crude wood-cuts, 

 the accompanying drawings of the specimen have been prepared 

 (Plates III and IV). With the following description, they make 

 plain the evident fact that Perosuchus is simply an abnormal 

 Caiman. 



Description of the type: Upper jaw with twenty teeth on the left side, 

 and nineteen on the right side. Lower jaw with eighteen teeth on each side. 

 Fourth maxillary tooth on each side larger than third. Width of head half 

 its length. Snout in form of rather broad isosceles triangle, as seen from 

 above, and its basal width a little less than its length. No strong ridges on 

 surface of snout; tip of snout with large convexly elevated prominence. 

 Orbit not produced in front. Interorbital space concave, narrow. Upper 

 eyehd of tough coriaceous tissues. Supra-temporal fossae prominent. 

 Two transverse rows of smaller post-occipital plates, and those in first 

 row larger, though scarcely half size of nuchals. Four rows of large 

 nuchals, all articulated with one another; first three rows, of four scutes; 

 and fourth, of two scutes only. Back covered with nineteen transverse 

 rows of scutes, the widest rows with seven or eight scutes each. The 

 median rows of scutes less carinate than those on either side. Tail with 

 thirty transverse rows of scutes. At eighteenth transverse scute, counting 



» Cat. Chelon. Rhyn. Crocodiles, Brit. Mus., 1889, p. 297. 



