136 LEIDY'S DESCRIPTION OF A NEW SPECIES OF CROCODILE. 



These may or may not be new species of extinct crocodile, for it is by no 

 means established that the vertebrae upon which they were founded do not belong to 

 the Crocodilus macrorhynchus of Harlan and the Crocodilus clavirostris of Morton. 



Should, however, all the above species of Crocodile which have been proposed, on 

 further investigation prove to be distinct, which is not probable, then there exist in 

 the cretaceous formation of New Jersey the remains of five species of extinct 

 Crocodile or Alligator constructed upon the existing type, and varying but little 

 in point of size. 



The discovery of a single tooth often serves to establish a new species or genus of 

 animals; a vertebra from the same locality in which the tooth was found may 

 characterize a second ; a fragment of a rib or a phalanx a third, and so on ad infinitum, 

 until some explorer happily succeeds in finding a whole or the greater part of a skeleton, 

 to different parts of which the descriptions of the previously discovered new species 

 and genera from the same locality so well apply, that all the names succeeding the 

 first fall to it as synonyma. 



With these prefatory remarks upon Crocodilian remains of the cretaceous period of 

 the United States, I come next to the particular subject of the present memoir, which 

 is an account of some remains of the Crocodile from the Miocene formation of Virginia. 



These remains consist of two teeth, two vertebree, a fragment of a rib, and an ungual 

 phalanx, which were found in association with some Cetacean bones, part of which 

 I have lately characterized as having belonged to an extinct species of whale with 

 the name Balsena palaeatlantica, also with Pecten JefFersonius, etc. 



They were discovered in the High-Cliffs of the Potomac River, 40 miles above the 

 mouth of the latter, in Westmoreland County, Virginia, by Mr. Robert H. Nash, who 

 kindly presented them to the Museum of the Academy of Natural Sciences. 



One of the teeth, represented in figure 1, Plate XVI, is a little less in breadth than 

 the first anterior inferior tooth of the adult Crocodilus biporcatus. In the specimen 

 the lower part of the fang has been broken away, but the tooth appears to have been 

 as long, or nearly so, as that referred to of C. biporcatus. It is slightly less curved 

 than that of the latter, and the crown, though as long, is much less robust, more 

 slender, less curved, and more pointed at the summit. The enamel is more finely 

 and sharply striated and at the apex of the crown is not so rugous, and its lateral 

 carinated ridges are not so elevated and extend but a relatively short distance below 

 the point of the tooth ; upon one side disappearing entirely nine lines from the 

 commencement, and on the other after five lines only. The fang is simply cylindrical 

 and invested by a thin lamina of osteo-dentine continuous with the basal edge of the 

 enamel. The large conoidal pulp cavity of the tooth extends to within eight lines 

 of the summit of the crown. Within this cavity, in the specimen which was not at all 

 worn off from use, was already formed a young tooth, represented in figure 2, closely 

 corresponding in form with the half inch of the summit of that which ensheathed it. 



