244 University Geological Survey of Kansas. 



size probably belong with the others. It is possible that some 

 of these teeth may belong with P. poly gyrus. 



The other described species of this genus are the following : 



Ptychodus mammilaris Agassiz. — Senonian, Turonian, and Cenomanian, 

 Europe. 



Ptychodus rugosus Dixon. — Senonian, England. 



Pti/chodus decurrens Agassiz. — Senonian, Turonian, and Cenomanian, 

 Europe. 



Ptychodus multistriatus Woodward. — Senonian and Turonian, England. 



Ptychodus latissimus Agassiz. — Turonian and Senonian, Europe. 



Ptychodus papillosum Cope, Cret. Vert. 294. — Upper Cretaceous, Colorado. 



Ptychodus triangularis Reuss. — Upper Cretaceous, Bohemia. 



Ptychodus levis Woodward. — Lower Chalk of England. 



SCYLLIIDJE 



The family Scylliidae comprises small sharks with sharp- 

 pointed cuspidate teeth, arranged in numerous series. The fol- 

 lowing genera are given by Woodward : 4 Paleoscyllium Wagner, 

 Lower Kimmeridgian of Bavaria; Scylliorhinus Blainv., Turo- 

 nian and Senonian ; Pristiurus Bonaparte, Lower Kimmeridgian 

 of Bavaria; Mesiteia Kramb., Senonian and Middle Eocene; 

 Chiloscy ilium Miiller and Henle, Molasse ; Crossorhinus Mailer 

 and Henle, Gault ; Cantioseyllium Woodw., Turonian ; Gingly- 

 mostoma Miiller and Henle, Danaian, Eocene. 



Numerous teeth from the Lower Cretaceous of Kansas seem 

 in all probability to belong in this family, and agree pretty well, 

 though rather large, with the teeth of Scylliorhinus, to which I 

 refer them provisionally. 



Scylliorhinus rugosus. Plate XXIV, fig. 5. 



Scyllium rugosum Williston, Kans. Univ. Quart., ix, p. 35. 



Central cusp broad, pointed, nearly symmetrical, the cutting 

 edges nearly straight, one of them a little longer than the other 

 and slightly convex near the tip ; a single pair of lateral den- 

 ticles, which are nearly equilaterally triangular in shape ; prin- 

 cipal cusp with six or seven strong ridges on the basal two-fifths ; 

 denticles with four or five similar ridges reaching two-thirds of 



4. Cat. Foss. Fishes Brit. Mus., I, p. 338. 



