WILLISTON : FISH TEETH FROM KANSAS CRETACEOUS. 29 



Jlesodon abra^us. 

 Mesodon abrasus Cragin, Colorado College Studies, V, lS9i. 



" This name is proposed for certain pycnodont teeth of low. rhom- 

 boidal form and feebly convex upper surface which occur in Xo. 3 

 of the Belvidere section, southwest of the Belvidere railroad station, 

 and seem to agree with the large mandibular teeth of Jfesodon. The 

 specific name refers to the occurrence in the tTi)e species of two 

 small, oblique facets produced at one end by attrition. The tr-pe has 

 a height (above root) of 3mm., a length of 13 mm., and a breadth of 

 •5 mm." 



"To the vomerine set of the same species may belong the rotund. 

 oval or nearly hemispherical teeth of similar height but smaller size. 

 which occur not uncommonly at the same locality and horizon, the 

 largest now available example of which measures about 6 and 7 mm. 

 in major and minor horizontal diameters." 



In the Xational Museum collection there are several teeth, occur- 

 ring singly, corresponding to the vomerine teeth described by Cragin. 

 That they belong with the other teeth there described is very doubt- 

 ful — indeed it is doubtful whether the other teeth belong with 

 Jlesodon, since it is impossible to locate the genus from single teeth. 

 It is not at all imix)ssible that the vomerine teeth are identical with 

 Cope's Jf. diastematicus . The larger teeth may be the same as those 

 of either the above-described species of Cijelodu^. 



The largest of the specimens in the present collection measures 

 10 by ~ih mm. : several smaller examples have diameters of 6 and 5 mm. 

 ( See plate XII, fig. 4. ) 



LEPEDOSTEID-E. 

 Lepidofii^t. sp. 

 In the National Museum collection there is a single exa:: : . : ?. 

 scute pertaining to some lepidotid fish (Xo. 1063, Kiowa shales). 

 Cope has described Jlac/tpUfius of this family from a stratum be- 

 tween the Upper and Lower Trinity Sands of Texas. It seems very 

 probable that the teeth referred to the vomer of Jfe^odon abra-^iis really 



belong here. 



MTLIOBATID-E. 



Pfi/chodus agas:<iz. 



Teeth with the crown more or less elevated and overhanging, orna- 

 mented with transverse or radiating ridges, and surrounded by a larger 

 or smaller, finely marked marginal area. Surface of the root smooth. 



This genus of Upper Cretaceous selachians was for a long time 

 placed among the cestracionts. but recent discoveries of the nearly 

 complete dentition render it more probable that the proper location 

 is with the Mvliobatid:^?. The livinsr Mvliobatidi^. or sea-devils, are 



