MOSASATJRUS. 37 



semblance, both in form and size, with one of the specimens figured by Dr. Gibbes 

 as characteristic of his Ampliorosteus Brumhyi} 



2. The bodies of two large cervicals or anterior dorsals. The specimens, together 

 with small fragments of a huge skull, were found in the first bed of Green-sand 

 at Holmdale, Monmouth County, N. J. They are too much mutilated for detailed 

 description, but are interesting on account of their size, as they measure a trifle over 

 four inches in length. From their under part projects a robust, cyluidroid hypapo- 

 physis, which, in both specimens, is broken at the extremity. 



3. A specimen consisting of a pair of large posterior dorsals or lumbars, and part 

 of a third with the bodies coossified by means of an irregular exostosis surrounding 

 the articular surfaces. It belongs to Eutger's CoUege, and though its locality is 

 xmknown, it is supposed by Prof Cook to have been derived from the deepest layer 

 of the Green-sand of Monmouth County, N. J. The anterior pair of vertebral 

 bodies together measure seven inches in length ; the anterior concave surface of the 

 first body is about four inches in diameter, and the vertebral canal, retained entire, 

 is transversely elliptical, and measures eleven lines wide and eight lines high. 



From Nebraska Territory, the museum of the Academy of Natural Sciences has 

 received a collection of remains of Mosasaurus, consisting chiefly of vertebrae, 

 which were discovered by Dr. F. V. Hayden. The specimens are as follows : — 



1. Several fragments of weather-worn rock, originally from the same mass, con- 

 taining a series of sixteen caudal vertebrse, two others of small size detached from 

 the series, and several bones of the extremities. The specimens were obtained on 

 the Yellowstone River, and the bones all appear to have belonged to the same 

 individual. The rock in which the fossils are imbedded bears some resemblance to 

 that described by Dr. Goldfuss, as containing the Mosasaurus skeleton from the 

 vicinity of the Big Bend of the Missouri River. It is a very hard, brittle, argilla- 

 ceous limestone, amorphous, and of a dark, dull leaden hue. On the surface it has 

 become softened, by the action of the weather, into a yeUowish-gray material. The 

 rock adheres so tenaciously to the equally brittle bones that they have been seriously 

 injured in the attempt to expose them. The vertebrae, several of which are repre- 

 sented in Figs. 15, 16, Plate VII, present the anatomical characters ascribed to the 

 posterior caudals of Mosasaurus by Cuvier, Goldfuss, and others. All had coossified 

 chevron bones ; and the anterior of the series have rudimental transverse processes, 

 which entirely disappear in the more posterior ones. The body of the first of the 

 series measures nineteen lines in length and twenty- three lines in height and width; 

 that of the last is fourteen lines in length and twenty lines in height and width. 

 The better preserved of the detached caudals, represented in Fig. 16, Plate VII, 

 has its body only nine lines in length. 



2. Two bodies of posterior caudals, weU preserved, from Cheyenne River. They 

 had coossified chevron bones and no trace of transverse processes. They measure 

 fourteen lines in length, eighteen high, and nineteen Avide. One of the specimens 

 is represented in Figs. 17, 18, Plate VII. 



3. Two caudal bodies, of the same form as the preceding, but rather larger, from 



1 Mem. on Mosasaurus, Plate III, Figs. U, 15, 16. 



