426 On Ctenoptychius, Ctenopetalus, and Harpacodus. 
O. Stevensoni, St. J. & W. Paleont. Min. vol. vi. p. 383, pl. xii. 
fig. 15. 
CO. semicircularis, N. & W. Paleont. Illin. vol. i. p. 72, pl. iv. 
figs. 18, 18.4, 18 0. 
CO. Ordii, Davis, Quart. Journ. Geol. Soc. 1881, p. 422, 
pl. xxi. fig. 8. 
Genus CTENOPETALUS, Agass. ined. 
Gen. char. Teeth of small or medium size; crown broad, 
compressed, gently rounded in outline; cutting-edge divided 
into from twenty to thirty small denticles; base of crown 
possessing three or four imbricating ganoine folds descending 
lower on posterior than anterior surface ; root narrower than 
crown, flattened, and about equal to it in height. 
Ctenopetalus ( Ctenoptychius) serratus, Agass. ined. (‘I'ype.) 
M‘Coy, Brit. Paleoz. Foss. p. 626, pl. 31. figs. 21, 
22, and 23 (Owen, Odont. p. 62). 
O. (Ctenoptychius) denticulatus, Agass.? Poiss. Foss. vol. i. 
pe LOW) ple xix ties: O-7- 
C. vinosus, St. J. & W. Paleont. Ilin. vol. vi. p. 396, pl. xu. 
fig. 13. 
C. occidentalis, St. J. & W. Paleont. Ilin. vol. vi. p. 401, 
pl. xu. fig. 14. 
Genus HArpacopus, Agass. ined. 
Gen. char. Teeth small ; crown slightly convex, strong ; cut- 
ting-edge very slightly circular, divided into from five to eight 
deeply-cut, broad, and strong denticulations; base of crown 
prominent, with a single broad fold of ganoine deeper pos- 
teriorly than in front; root at its junction with the crown 
much constricted; lower it is expanded, large, and tumid. 
Harpacodus (Ctenoptychius) dentatus, Ag. med. (Type.) 
H. ne apicalis, M‘Coy, Brit. Paleoz. Foss. 
p- 626. 
H. ( Ctenoptychius) macrodus, Ag. ined. 
H. ( Ctenoptychius) macrodus, Portl. Geol. Rep. p. 467, pl. xiv. 
fig. 7. 
H. (Ctenoptychius) pectinatus, Ag. Poiss. Foss. vol. i. p. 100, 
pl xix igs. 253. 
FH. (Petalodus) dentatus, Owen, Odont. p. 62. 
H. ( Ctenopetalus) limatulus, St. J. & W. Palzont. Ilin. p. 399, 
ple xaos Se 
H. ( Ctenopetalus) medius, St. J. & W. Paleont. lin. p. 400, 
pl. x. A. fig. 26. 
H. Ce pectinatus, Davis, Q. J. G. 8. 1881, 
p. 424. 
