MOSASAURUS. 39 



negative evidence with the ichthyc character of the tail, and suspected that per- 

 haps as in fishes, the vertebrae of Mosasaurus were developed from single centres of 

 ossification. If such were the case, mere differences m size of corresponding ver- 

 tebrae would not be sufficient to determine a difference of species. 



Frdfei Prof. George H. Cook, of Eutger's College, New Brunswick, N. J., I have 

 recently received, for examination, a number of remains of the Mosasaurus, from 

 the Green-sand of Monmouth County, N. J. Among them is a collection, consist- 

 ing of a multitvide of small fragments of a skull, from the Marl digging on the 

 farm of Isaac Smock, of Holmdale. The best preserved of the fragments consist 

 of the greater part of both quadrate or tympanic bones, and the anterior extremity 

 of the face or muzzle. The tympanic bones agree in form with the corresponding 

 parts of those of the Maestricht skuU preserved in the Paris museum. They 

 measure about six inches in height, so that they are somewhat smaller than in the 

 latter specimen. 



The anterior extremity of the face, represented in Fig. 6, Plate XIX, consists 

 of the forepart of the right maxillary bone, and nearly the entire intermaxillary 

 bone. The end of the snout, as formed by the latter, is a demi-cone, with the flat 

 surface comprising the forepart of the mouth. The height, breadth, and length of 

 the demi-cone are nearly equal, being about three inches. The intermaxillary bone 

 is prolonged upward and backward, and ends in a narrow process contributing to 

 the partition of the anterior nares. It contains on each side of the palatine surface 

 the fangs of two teeth, together with cavities for successors. It would thus appear 

 that the number of intermaxillary teeth in Mosasaurus is one less on each side than 

 supposed by Cuvier, though his numeration applied to the Maestricht Mosasaurus, in 

 which species the number may have been greater than in the New Jersey Monitor- 

 In one respect the fossil appears to differ from the corresponding portion of the 

 Upper Missouri skull, described by Dr. Goldfuss. In his, Plate 7, Vol. XXI, of 

 the Nova Acta, representing a lateral view of the skull, the intermaxillary is not 

 visible above the border of the maxillary bone, but is so in the New Jersey fossil, 

 as seen in Fig. 6, Plate XIX of this memoir. 



The forepart of the maxillary bone has lost the end which unites it with the 

 alveolar border of the intermaxillary corresponding in extent to the position of the 

 first maxillary tooth. Behind the latter the fossil contains the fangs of the four 

 succeeding teeth. Accompanying the specimen are other fragments of the alveolar 

 border, together measuring a foot in length, and occupied by the fangs of seven 

 teeth, but not fitting from the loss of an intervening portion. About an inch above 

 the alveolar edge there is a longitudinal row of large vasculo-neural foramina, which 

 communicate with a canal situated along the outer part of the bottoms of the fangs 

 of the teeth. Similar foramina form a row along the intermaxillary bone near its 

 upper boundary. The anterior extremity of the nares, seen in the fossil, corresponds 

 in position with the interval between the fifth and sixth maxillary teeth. 



The length of the fossil, from the end of the snout to the posterior broken ex- 

 tremity, is ten and a half inches ; the distance from the end of the snout to the 

 anterior nares is ten inches. 



Another collection, received from Prof. Cook, consists of fragments of the forepart 



