20 KANSAS UNIVERSITY QUARTERLY. 



backward from the extremity of this portion there is a row of large, 

 shallow foramina, the posterior ones of which have shallow grooves 

 leading into them from behind. Below this line of foramina the 

 bone is not so thick, and is covered with numerous fine striae. 



The superior portion has a rather broad process extending up- 

 ward, formed by the anterior and superior borders The posterior 

 portion of the bone is thin and striate on both sides of the. upper 

 portion. 



The bone figured by Cope* and described by Crookf as an inter- 

 opercular I am inclined to think is not an opercular bone but one 

 of the cerato-hyals. I have found a bone very similar to this be- 

 tween the lower jaws of a specimen of Anogmius { B cry x) poly mi- 

 crodus Stewart, and another, somewhat different though bearing a 

 general resemblance to it, between the lower jaws of a specimen of 

 Ichthyodectes. With this evidence at hand, there can be but very 

 little doubt of its being a cerato-hyal. The bone is elongated and 

 in outline is somewhat the shape of a parallelogram with one side 

 crushed in. The posterior end is the broader of the two and bears 

 an elongated, narrow and concave facet for the epi-hyal. The an- 

 terior end is more irregular in outline and bears two facets for the 

 hypo- and uro-hyals. The bone is thin and finely striated through- 

 out. 



There is still another opercular bone, which I regard as a sub- 

 opercular. The bone is broad and flat, thin along the borders and 

 thickened toward the central portion. The posterior extremity is 

 the broader of the two and is somewhat rounded. The anterior 

 end is much more narrow and bears a small elliptical facet on a 

 slight elevation of the bone. It also presents a beak-like process, 

 separated from the above by a slight depression. Both the external 

 and internal sides are striated, the striae becoming very pronounced 

 near the posterior end of one of the sides. 

 Measurements of the opercular bones: 



Opercular; length of anterior border 373t nim. 



" length of anterior border below the facet for 



the h3'omandibular 268 



" length of facet for the hyomandibular 55 



" transverse width of facet 22 



Preopercular; greatest length 345 + 



" width near superior extremity 80 



" width of inferior end i7o| 



*Cret. Vert. West., pi. XL. flg. 

 tPaleontojrraphica, 1893, p. IIT. 

 fEstimatt'cl. 



