306 University Geological Survey of Kansas. 



the mouth must have been rather small. The maxillae of typ- 

 ical species of Ichthyodectes are nearly straight along the tooth 

 line, or sinuous, or, in I. hamatus, strongly concave. In /. 

 polymicrodus the tooth line is strongly convex, except just be- 

 hind the palatine condyle. The teeth of I. polymicrodus are 

 numerous and feeble ; in the other species, strong and in small 

 number." 



Gillicus arcuatus. Plates LII, LIII, and LIV. 



Portheus arcuatus Cope, Cret. Vert. West., pp. 204, 274, pi. xlvii, figs. 7-9. ^ 

 Ichthyodectes arcuatus Cope, Proc. Am. Phil. Soc. 1878, p. 177; Amer. 



Nat., vol. xvn, p. 942. 

 Ichthyodectes polymicrodus Crook, Paleonto., 1892, p. 112, pi. xvi. 

 Ichthyodectes arcuatus Cope, and Ichthyodectes polymicrodus Crook 



and Hay, Amer. Jour. Sci., vol. vi, p. 228. 



This species is represented in the museum by the remains of 

 three individuals with the skull in good condition, and frag- 

 ments of several more. 



The maxilla is a broad and thin bone, with the greater part 

 of the alveolar border very convex. Just back of the surface 

 for the premaxilla this border is directed sharply upward, form- 

 ing a rather deep concavity near the anterior end, back of which 

 it is gently curved. This border gives support to a single row 

 of minute teeth, which are bent slightly inward at the apices. 

 Doctor Crook says that twenty-four of these occur to the centi- 

 meter, in which I am inclined to think that he is mistaken, unless 

 he intended it to apply to the posterior end, where the number 

 will probably reach that many, but at the anterior extremity I 

 have been unable to make out more than from seventeen to 

 eighteen. The surface for the premaxilla is bent inward to a 

 considerable extent and is separated from the alveolar border 

 by a slight notch inferiorly. The condyle for the palatine is el- 

 liptical in outline, slightly convex, and elevated slightly above 

 the rest of the bone. Professor Hay was able to distinguish 

 some differences in the form of these condyles, as he says : 66 " In 

 looking over my specimens it seems to me that I can observe 

 characters that indicate two species. In one maxilla I find that 



65. It is doubtful if these figures refer to this species 



66. Amer. Jour. Sci., VI, p. 229. 



