NATURAL SCIENCES OF PHILADELPHIA. 203 



On the Crocodilian genus PEROSUCHU S. 

 BY EDWARD D. COPE. 



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 fingers and half webbed toes, and 

 the bony abdominal buckler, together with the cartilaginous nasal septum are 

 points of strong resemblance to Jacare (Gray, including Cxman Gray), but it 

 differs from these creatures in the lack of bony orbital plate. In specific cha- 

 racters it differs from those of this genus, which it most resembles, as J. n i- 

 gra, 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 it 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 alliga- 

 torial, I am disposed to anticipate that the dental arrangement of the latter 

 type will be most common. 



Perosuchus fdscus Cope. 



Char, specificus. — Nuchal plates in a cross row of six ; cervicals in four 

 cross-rows, all of four plates except the last of two. Dorsal plates six — in 

 a few eight in each transverse row. No posterior crest on arm or leg. Tail 

 short with remarkably low crest. Muzzle broad, flat, without any ridges ; 

 its width at the eighth tooth entering 1-4 in length from end of 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 lin. ; and the tail from the vent 13 in. 

 1 line. From groin to heel 3 in. 2-5 lines, and the hind foot 2 in. 7-5 lines. 

 The muzzle is a broad ovate, the sides rather more convergent anteriorly 

 than in the Alligator mississippiensis. There is a thickening in front 

 of each orbit, and between them on the middle line another, which together 

 enclose two shallow concavities. Superciliary margins raised, the cranial 

 table quite flat. The margin of the quadrato-jugal bone projects strongly. 

 The scales of the limbs are all smooth and those of the dorsal region with 

 very low keels. The sides have four longitudinal rows of ovate scales sepa- 

 rated by scarcely defined smaller ones. The abdominal plates are longer 

 than broad, and are in twelve longitudinal rows. Dorsals in seventeen 

 transverse series from interscapular to crural region. The lateral crests of 

 the tail are only obtuse keels ; they unite on the thirteenth aunulus behind 

 the vent inclusive. Color above dark brown, almost black on the upper sur- 

 face of the head. The tail is paler, of a liglit olive brown. Lower surface 

 everywhere bright yellow, including the entire lower jaw and margin of the 

 upper. Eyelids and a band through ear yellow, the former with a black spot 

 above. 



Remarks. — This interesting addition to our knowledge of the Reptilia was 

 made by Schulte Buckow, of New York, while on a visit to the interior pan 

 of the course of the Magdelena River, in New Grenada. This naturalist 

 has also enriched our collections with other interesting vertebrata of that 

 region, both living and dead. 



1868.] 



