210 



M. 



Doi>th of tho maxillary at tlio condyle ^ 0. ((27 



Depth of tbo maxillary behind the condyle fl. 02:i 



Depth of the maxillary near the middle (I. 0:i7 



Width of the ventral spine 0. O.U 



This S2)ecies and the two preceding were not very unlike in size ; the 

 two following are smaller. 



ICHTHYODKCTES PROGNATHUS, (JopC. 



Proceedings of tho American Philosophical Society, 1870, November {Sauiocephahis) ; Hayden's Geologi- 

 cal Survey of Wyoming, &c., 1871, p. 417. 



In this species, the premaxillary is more rhomboid in outline than in the 

 others, and is less convex externally. Of its more numerous teeth, the first 

 is not larger than the last, differing thus from all others of the genus; it is in 

 line with the nearly straight anterior margin of the bone, and is more com- 

 pressed than in the other species. The surface of the l)one is peculiar in a 

 minute sculpture of impressed lines, or lines oC punctae. There is a very 

 small articular surface on the superior extremity. 



This species is represented by a premaxillary and attached proximal 

 j)ortion of the maxillary l)oiies of the right side, and by a large number of ver- 

 tebra; and other bones. These portions were associated in the collections 

 placed in my hands by Professor Mudge, and relate to each other in size, as 

 do those of the preceding species and the Ichthyodectes ctenodon. 



The premaxillary is characterized by its great depth as compared witli 

 its length, and by the shortness of its union with the maxillary. The pala- 

 tine condyle of the maxillary reaches a point above the middle of the alveolar 

 margin of the premaxillary. The latter contains alveolae of seven tectli, the 

 anterior of which only presents a perfect crown. It is elongate, compressed, 

 equilateral, smooth, and acute. Its direction is even more obliquely forward 

 than the anterior outline of the bone, which tself makes an angle of 50° 

 with the alveolar border. 



The vertebrae consist of cervicals, dorsals, and caudals, to the number 

 of about sixty, most of which are supposed to have been derived from the 

 same animal. The grooves are as in D. phlebotoinus ; there being two below, 

 two on each side, and two above. The latter receives the bases of the neu- 

 rapopliyses, which are in many cases preserved. The inferior pair of grooves 

 becomes more widely .separated as we approach the cervical series, leaving 

 an inl'erior plane, which is longitudinally striate-grooved. This plane widens 



