240 University Geological Survey of Kansas. 



tulation, clearly visible only with the aid of a lens, giving a 

 uniform, finely roughened appearance. The median upper row 

 is composed of low, flattened teeth, transversely oval or sub- 

 quadrate in shape, with a slight elevation in the middle, and 

 finely roughened throughout the whole coronal surface, there 

 being only the slightest trace of the divergent ridges on the 

 summit of the elevation. This does not quite agree with Wood- 

 ward's description of these teeth, in which he states that they 

 are "not marked with the radiating ridges, but exhibit a mi- 

 nute smooth eminence in the middle of the crown." Possibly 

 this effect is due to wear. 



Ptychodus polygyrus. Plate XXIX, fig. 9: plate XXX, fig. 14. 



Ptychodus poly gyrus (Buckland) Agassiz, Poiss. Foss., in, p. 156, pi. xxv, 

 ff . 4-11, pi. xxv-b, ff . 21-23 ; Gibbes, Journ. Acad. Nat. Sci. Phil. , i, p. 299, 

 pi. ii, ff. 5,6; Leidy, Proc. Acad. Nat. Sci. Phil. 1868, p. 208; Cope, Cret. 

 Vert., p. 291; Woodward, Cat. Foss. Fishes Brit. Mus., i, p. 143, pi. v, 

 f. 7 — Senonian, Turonian of Europe, Rotten Limestone of Alabama, 

 Niobrara of Kansas; Williston, cf. cit. 31. 



? Ptychodus latissimus Agassiz, 1. c, fig. 8; Dixon, Foss. Sussex, pi. xxx, 

 ff. 1, 2. 



A single tooth of very large size from the lower beds of the 

 Niobrara Cretaceous of the Smoky Hill river is referred to this 

 species provisionally. Until numerous specimens are examined 

 there can be no certainty of its correct location, though the re- 

 semblances are sufficiently great to render the determination 

 not improbable ; at least with some of its varieties. 



Ptychodus martini. Plate XXVIII. 



Ptychodus martini Williston, cf. cit. 32. 



A large series of teeth, 110 in number, found together in the 

 Niobrara chalk of the Smoky Hill river, and collected by Mr. PI. 

 T. Martin, cannot be identified with any described species. I 

 have photographed them, arranged as symmetrically as possible, 

 but with no assurance that the arrangement is a natural one. 

 In fact, it is not improbable that the teeth belong to both upper 

 and lower jaws. The teeth apparently from the lower median 

 row are much elongate transversely, with a very flat crown, 

 wherein they differ from the teeth of other known species. The 

 ridges are nine or ten in number, and reach nearly to the lateral 



