MOSASAURUS. 39 
negative evidence with the ichthye 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 in size of corresponding ver- 
tebree would not be sufficient to determine a difference of species. 
From Prof. George H. Cook, of Rutger’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 multitude 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 skull 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 Mosasawrus 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. X-XI, 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 
