346 GEOLOGICAL SUEVEY OF THE TEKEITOEIES. 



Premaxillary with a single large tooth ; dentary with an 

 outer row of small and an inner row of large teeth, 

 which are much larger at the distal end Encliodus. 



STEATODUS, Cope. 



This genus is well characterized by its dentition, which is remarkable 

 for the small size and large number of the teeth, and their peculiar form. 

 I possess one premaxillarj^, a considerable part of the maxillary, and 

 nearly the whole of both palatines, besides other bones, of one species. 

 These were found not very far from the remains of the Cimolichtkys 

 semianceps, M., and it required some investigation to determine the 

 relationship between them. I have, however, portions of the maxillary 

 and premaxillary of CimoUchthys, and both of these elements are so 

 very unlike those in Stratodus that there can be no doubt of its inde- 

 pendence. I have unfortunately no dentary bone of Stratodus, and the 

 outer row of palatines resembles, in some measure, those figured in 

 Ciniolichtliys levesiensis, Leidy, by Agassiz. 



The premaxillary teeth are in two series. They are stout at the base 

 and oval in section, and are contracted and flattened rapidly upward. 

 On this basis is set an oval, sharp-edged, flat or spade-shaped crown, 

 the long axis of compression being placed at right angles to that of the 

 compression of the apex of the base. This gives a barbed appearance. 

 The maxillary teeth are similar in form, but are in but few rows. The 

 palatine teetb are constructed on the same plan, but they are longer, 

 and the bases are subcylindric and slightly curved. All the teeth pos- 

 sess a large pulp cavity. 



The premaxillary bone displays some of the density of composition 

 seen in Encliodus. Its upper anterior surface meets the inferior at an 

 acute angle. It is a broad oval, and is slightly concave. The inner 

 face forms a truncate rim round the bases of the inner teeth, and ter- 

 minates in a vertical crest of dense bone. The external face is, on the 

 other hand, perpendicular, and extends obliquely upward and back- 

 ward. An acute anterior angle of the maxillary underruns it below, so 

 far as to exclude all but one or two of the premaxillary teeth from the 

 outer row. The external lamina of the premaxillary forms an extensive 

 squamosal suture with this part of the maxillary by overlapping it from 

 above. This arrangement shows a certain similarity to Esox, especially 

 in the large number of palatine and small number of maxillary teeth. 

 It differs materially in the lack of articular surfaces between the maxil- 

 lary, palatine, &c., in the upward prolongation of the premaxillary, and 

 the peculiar forms of the teeth. 



OIMOLICHTHYS, Leidy. 



Proc. Acad. Nat. Sci., Pliila., 1856, 302 ; Trans. Amer. Philos. Soc, 1856, jj. 95 ; Saurodon, 



Agassiz, pt. Poiss. Foss. 



In this genus the principal teeth are stout, and have a compressed 

 apex, with a prominent anterior cutting edge, and a less extended pos- 

 terior one. There are several series of smaller teeth, external to the 

 large ones in the lower jaw, while in a portion of an upper jaw of one 

 of the species these are wanting. Where present, they are more acute 

 than the larger ones. The large teeth diminish gradually in length to 

 the symphysis, a circumstance which separates these fishes from 

 Encliodus, where one or more of the anterior teeth are elongate. In 



