225 



form is very different from that in P. caninus, where the symphyseal surface 

 is subround. 



The anterior teeth are smaller than the median, and have the inner 

 alveolar wall nearly as much elevated as the external. The crowns are 

 scarcely distinguishable from those of the P. caninus, being curved-conic, 

 with round section and smooth cementum. They form an incurved row next 

 the symphysis, and a single tooth stands within the anterior one. Number 

 of teeth in an inch at middle of ramus, 4.5. 



Pachyrhizodus sheareri, Cope. 



Associated with the bones of the P. caninus is a slender bone of oval 

 section, which is marked on one edge by twenty-two transverse alveoli, whose 

 outer margins are a little higher than the inner. No teeth preserved. It may 

 belong to a fish of this genus, and is probably a superior maxillary bone. 

 Consistently with this position, its outer extremity is more compressed than 

 the proximal; the thickening being especially seen in the superior margin. 

 A shallow concavity passes obliquely across this border from within outward 

 and distally, as in P. caninus; but the articular face is not preserved. There 

 is a longitudinal angle on the external face ; and the superficial layer of bone 

 is nowhere grooved or rugose. The pleurodont character of the tooth- 

 attachment is more marked proximally. Length of piece, m .041 ; vertical 

 diameter, m .007 ; greatest transverse diameter, m .0033. 



This species is dedicated to Doctor Shearer, assistant post-surgeon, to 



whose interest in the subject the geology of Kansas is indebted to many 



useful discoveries. 



Pachyrhizodus leptopsis, Cope. 



Represented by portions of the right and left dentary bones, with other 

 portions of the cranium. The symphyseal part of the ramus is not incurved 

 as in P. caninus and P. kingii, but is obliquely truncate, indicating that the 

 chin had a compressed form, and was not rounded, as in them. The lower 

 portion of the bone is thin and laminiform, to a deep groove, which extends 

 from the edge of the symphyseal face, along the inner side, at one-third the 

 depth of the ramus from the inner bases of the roots of the teeth. The 

 latter are thus supported on a thickened basis. They are rather remote in a 

 functional condition ; each interspace being entirely occupied by the alveolar 

 fossa of the shed tooth. These bases are very stout, and composed of dense 

 29 c 



