276 



The neural arch exliibits rudiments of zygapophyses. The bottom of the 

 body is provided with a pair of deep, conical pits for the attachment of a 

 chevron-bone. The pits are defined with a prominent margin most project- 

 ing anteriorly. 



The measurements of the specimen are as follows : 



Lines. 



Leugth of the body inferiorly 20 



Diameter of the body at the extremities 30 



Of the two specimens of teeth, one is crushed nearly flat; the other, well 

 preserved, is represented in Fig. 3. It presents the usual form more or less 

 characteristic of Mosasaurus. It is curved conical, with the inner and outer 

 surfaces defined by acute ridges. The surfaces ai-e subdivided by longitudinal 

 ridges, becoming obsolete toward the point of the tooth. The intervals of 

 the ridges are feebly concave and faintly rugose. Internally near the base 

 they are delicately striate. 



The length of the crown externally is 20 lines ; the diameter at base is 10 

 lines. 



Several additional specimens, apparently belonging to another individual, 

 consist of small fragments of jaws and palatine bones with bases of teetli. 

 Among the" specimens is a portion of a splenial bone, with" its posterior artic- 

 ular surface nearly entire, as represented in Fig. 13, Plate XXXV. The 

 articular surface is a pyriform excavation, with a ridge descending from the 

 upper part internally to near its center. 



LESTOSAURUS. 

 Lestosaurus coryph^us. 



Dr. Sternberg's collection of fossils from the Smoky Hill River, of Kansas, 

 belonging to the Smithsonian Institution, contains numerous specimens of 

 dorsal vertebrae of a mosasauroid, which have the appearance as if they had 

 pertained to a single individual. There are about fifty of these vertebras, 

 but all have been more or less compressed from pressure of the superincum- 

 bent beds to that in which they lay, so that not a single specimen preserves 

 the exact original lorni. They ditfer but little in size, the more anterior 

 being somewhat shorter than the others. 



The specimens appear to belong to the animal described by Professor 

 Cope under the name of Holcodus corypliceus, which Professor Marsh has 

 referred to another orcnus with the name of Lestosaurus. 



