196 PROCEEDINGS OF 



A fourth species, consisting of a portion of the superior jaw, has been found in 

 the calcaire grossier, in the department of Orue. 



M. Cuvier has been able to satisfy himself that all these species are distinct from 

 each other, as well as from the living species. 



The specimen before us bears tiio nearest comparison with tlic first of the above 

 named species, but is sufficiently distinguished by the larger size, relative proportions, 

 and number of teeth of the Appeninc species. 



Description of D, Calvertcnsis. — In general outline, resembling other skulls of 

 this genus. The head is proportionably narrower, and snout more elongated, than 

 tlie Italian specimen with which I have compared it. The occipital and temporal 

 ridges are strongly developed, indicating muscular strength, especially of the jaws. 

 We find similar indications in the remains of the teeth, which have been large and 

 robust. There are ten sockets remaining on the right side, with the teeth broken 

 otf at the rim. Thesa organs approximate each other. The ton sockets include a 

 lino four and a half inches long. There has been about one and a lialf inches of 

 the end of the snout broken off, which would afford room for two or three more 

 teeth — making twelve or thirteen, in all, on each side. The pyramidal eminence, 

 anterior to the posterior nares, on the palatine surface, is strongly pronounced. It 

 terminates opposite the last tooth. The excavations or longitudinal grooves, on 

 each side of the upper portion of this eminence, are unusually deep. The palatmo 

 surface is slightly convex transversely. Above, tho head is narrower across the 

 occipital ridges than otlier allied species, and narrower than the* transverse diame- 

 ter of the base of tho skull. The ossa nasi are longer than broad, and convex. 

 The atlas vertebra adheres to the occiput, abovo the condyles. It measures, across 

 the transverse processes, five inches ; transverse diameter, tlireo inches ; and the 

 ring is about one inch thick. 



In tho following admeasurements, one and a half inches must bo considered as 

 the length of the last portion of the extremity of the snout. 



Dimensions. — Total length of head, from the temporal crest to the presumed ex- 

 tremity of tho jaw, - - 17 inches. 



From tiie anterior borders of the spiracles to the presumed ex. 

 tromity of snout, .-..--.-.- 11.5 inches. 



Breadth of skull above, across tho occipital crests, . - - 5 inches. 



Breadth at base, between the temporal bones, . - - • 6.5 inches. 



Longest diameter of largest tooth at the socket, ... 34 tenths. 



Tho head of the Appenine species is ono foot, ten inches, nino lines long, French 

 measure. Tlic spiracles are ono foot nine inches, from tho extremity of tho snout. 



The accurate figures which accompany this description, will render further do- 

 tails unnecessary. 



Geological Series: Middle tertiary of Maryland. 



Description of the Plates. 

 Figure 1 — Basal view of the skull. 

 Figure 2. — Superior view of tho skull. 

 Fi^ro 3 — Lateral view of the skull. 

 Figure 4.— Occipital view of tho ukull. 



