THORACOSAURUS. 



SAUEIA. 



TH0ESAC08AIJRCJS. 

 Thoracosauru§ neocesariensis. 



New Jersey Gavial, De Kay, Ann. Lye. Nat. Hist. N. Y. Ill, 1833, 156, pi. iii, figs. 7-10. 



Gavialis neocesariensis, De Kay, Zool. New York, 1842, part III, 28, pi. 22, fig. 59. 



Crocodilus s. Gavialis clavirostris, Morton, Proo. Acad. Nat. Soi. Pbila. Ill, 1844, 82. — Giebel, Fauna d. Vorwelt, 



1847, 122. 

 Crocodilus basijissus, Owen, Jour. Geol. Soo. Lond. V, 1849, 381, pi. x, figs. 1, 2 ; Palaeontology, 1860, 277. — Pictet, 



Traite de Palffiont. I, 1853, 482. 

 Sphenosaurus, Agassiz, Proo. Acad. Nat. Sci. Phila. IV, 1849, 169. 

 Thoracosaurus grandis, Leldy, Proc. Acad. Nat. Sci. Phila. VI, 1852, 35. 



The most characteristic of the Crocodilian remains, obtained from the strata of 

 the Cretaceous period in the United States, consists of a nearly entire skull, which 

 was discovered in limestone, overlying the ferruginous Marl, on the farm of Gen. 

 William Irick, near Vincenttown, Burlington County, N. J. The specimen was 

 j.i'csented by that gentleman, and Mr. Wm. Whitman, of this city, to the Academy 

 of Natural Sciences, in the cabinet of which it is now contained. This finely pre- 

 served fossil consists of the skull, without the lower jaw. It has lost the anterior 

 extremity of the muzzle, estimated to have been equal to half its original length. 

 The teeth are also broken away, but sockets with the remains of fangs for fourteen 

 of the back teeth exist on each side of the fossil. The zygomatic arches, as formed 

 by the squamosals, are broken away, as is also the case with the articular ends of 

 the tympanies and the lower or outer conjoined extremities of the ecto- and ento- 

 pterygoids. 



The matrix, in which the fossil was imbedded, for the most part has been chiselled 

 away. Portions still adherent and occupying one orbit and palatine orifice, besides 

 the interior of the cranium and nasal passages, consist of a moderately hard, gray 

 arenaceous limestone. The bones of the fossil are brown and friable. 



In general shape and construction the fossil skull exhibits more resemblance to 

 that of the existing Gavial of the Ganges (Gavialis Ga^igeticus) than of any other 

 of the living crocodilian Reptiles, though from the non-eversion of the orbits and the 

 more gradual prolongation of the muzzle it also presents a relationship to the genus 

 Mecistops, of Western Africa. Of all known forms, however, it bears most resem- 

 blance to the skull of the extinct Gavialis macrorliynchus, of the Cretaceous forma- 

 tions of Europe. 



In consequence of the anterior extremity of the muzzle being lost in the Ncav 

 Jersey specimen, we have no positive means of ascertaining the length of the skull . 

 Supposing it, however, to have held the same relation of length to breadth as in the 

 recent Gavial, in its perfect condition it would have measured about three and 

 three-quarter feet in length and one and a-half feet in breadth. The relation of 

 length to breadth in the Gavialis macrorhynclius, with which the New Jersey 

 species appears to be most closely allied, is rather less, and would have made our 



