Williston.] Cretaceous Fishes. 241 



margin. In some of the teeth several of the ridges form loops 

 near the extremities. The marginal area of granulations is 

 small, and presents scarcely any distinct vermiculations. The 

 teeth of the lateral rows are less elongated than those of the 

 middle one, though still more so than is usual. The granula- 

 tions become rather more extensive in area proportionally in 

 the small teeth, as is the case with other species. A series 

 (left vertical row of the plate) that may belong in the medio- 

 lateral rows of the upper jaws are more nearly square in'shape, 

 and the crown has a distinct, though low, convexity extending 

 over nearly its whole area. Antero-posteriorly the surface is 

 nearly Hat, with a moderate convexity of the margin. The 

 surface posterior to the large grooves on the upper part shows 

 small, radiating and branched ridges. 



The largest teeth measure 45 by 20 mm. ; the ones more 

 nearly square, 35 by 25 mm. 



Ptychodus anonymus. Plate XXIX, figs. 5-3, 1(3-18, 20-22, 21. 

 Ptycliodus anonymus Williston, cf. cit. 32. 



S< ven teeth of nearly uniform size, four of them united in 

 the matrix, from Walnut creek, Kansas, seem to belong to a 

 species distinct from any previously described (figs. 16-18). 

 They are of about the same size as those described as P. whip- 

 pleyi and P. occidentalism but will be distinguished from the 

 former by the more broadly conical crowns. In the teeth of 

 this size of P. whippleyi the crown is much compressed, stand- 

 ing up, tooth-like ; in the present specimens they are nearly 

 straight or gently concave from the apex to the rims. From 

 P. occidentalis the species will be distinguished by the very dis- 

 tinctly reticulate marginal areas, the transverse ridges not 

 reaching to the rims of the crown. Other specimens agreeing 

 in these characters are from the Niobrara. The horizon is 

 probably Benton. 



