THORACOS AURUS. 9 



length and corresponds with that part of the jaw just in advance of the divergence 

 of the rami, and consists of portions of both dentals and splenials. The right dental 

 contains remains of four alveoli with portions of their teeth, of wjiich one incloses 

 the entire crown of a successional tooth. 



This fossil fragment of the lower jaw I suspect to belong to the same species as 

 the Vincenttown skull, but to a smaller or younger individual. The symphysis of 

 the splenials, preserved at the posterior part, in the perfect condition, is estimated 

 to have been about seven inches in length. The breadth of the jaw at the back 

 extremity of the symphysis of the splenials is estimated to have been about four 

 and a quajter inches ; and at the fore extremity two and three-quarter inches. The 

 oral surface of the splenials and dentals presents about the same degree of convexity 

 as in the recent Gavial. 



The cabinet of the ' Academy contains a fragment of the left upper maxilla, 

 apparently belonging to the same Gavial as the fossil skull just described, which is 

 of especial mterest from its retaining several entire and weU-preserved teeth. The 

 specimenj together with some small fragments of the jaw and teeth of the same 

 individual, were obtained by Dr. J. L. Burtt, from the Cretaceous limestone, near 

 Blackwoodtown, Camden County, N. J. The fragment to which we especially 

 refer, represented in Fig. 2, Plate II, is about eight inches long, and corresponds 

 with that portion of the left maxdla in the fossil skull which contains the back six 

 teeth with the exception of the one or two last ones. It has a portion of the malar 

 attached, and belonged to a rather larger individual than the Vincenttown skuU, for 

 it contains one tooth less in the space occupied by seven in the latter. 



The crowns of the teeth protruding from the specimen are curved conical as in 

 the recent Gavial, but are more robust in proportion with their length. The ridges 

 separating their outer and inner surfaces are also less prominent than in the living 

 Gavial. The more anterior of the teeth, towards the base of the crown, internally 

 exhibit a slightly fluted disposition. The enamel, which is jet black, is closely 

 striated longitudinally with fine linear ridges, and also presents a feeble annular 

 disposition towards the summits of the crowns. 



The measurements of the teeth, counting them from behind forward, are as 

 follows : — 



Lines. 



Length of crown of third tooth Yf 



Diameter of base from without inwardly . . . . . . . .5^ 



Length of crown of fourth tooth .10 



Diameter of base from without inwardly . . . . . . . . 6i 



Diameter of base at the divisional ridges Y-J 



Length of crown of sixth tooth ......... 13^ 



Diameter of base from without inwardly 8 



Diameter of base at the divisional ridges 9i 



Length of sixth tooth to bottom of alveolus 39 



Diameter of base of eighth tooth from without inwardly ..... 9^ 

 Diameter of base of eighth tooth at divisional ridges . . . . .10 



A detached tooth, represented in Fig. 4, Plate I, from the same individual as the 

 fossil fragment of jaw just described, presents the same characters as those contained 

 in the latter. 



2 March, 1865. 



