COCHLIODONTID^). 
217 
Dental plates differing from those of C. gibbus in the relatively 
less antero-posterior extension and the more rounded and prominent 
character of the coronal elevation. 
Form. Sf Loc. Upper Carboniferous Limestone : Yorkshire. 
P. 4908. Type specimen shown, of the natural size, in PI. VI. fig. 26; 
also a more imperfect dental plate : Yoredale Bocks,Wens- 
leydale. Horne Coll. 
49634. Uragment of dental plate ; Richmond. Purchased , 1878. 
According to the views of Agassiz, as interpreted by J. AY. Davis, 
the so-called genera Stenopterodus , Chitonodus, and Deltodopsis, 
proposed by St. John and Worthen (Pal. Illinois, vol. vii.), must be 
regarded as comprising miscellaneous dental plates of the various 
genera enumerated above. 
The dental plates of “ Stenopterodus” (tom. cit. p. 100) might 
well be assigned to Deltodus and “ Streblodus.” They are described 
under the names of S. elongatus (tom. cit. p. 106, pi. iy. figs. 1-3), 
from the Warsaw Limestone of Illinois ; S. planus (tom. cit. p. 102, 
pi. iv. figs. 9-14), from the Upper Burlington Limestone of Iowa 
and Illinois; and S. sp.? (tom. cit. p. 105, pi. iv. figs. 15, 16), from 
the Keokuk Limestone of Illinois. The type species of Sandalodus 
(S. parvidus, Newberry and Worthen) is also jfiaced here. 
The dental plates of “ Chitonodus ” (tom. cit. p. 109) seem to be 
assignable to Cochlioclus , Deltodus, Poeciloclus, and “ Streblodus,” 
and the genus is said (p. 112) to include Cochlioclus Icitus , Leidy, 
Poeciloclus rugosus, Newberry and Worthen, and P. orncitus, New¬ 
berry and Worthen. Pour other species are distinguished as fol¬ 
lows : C. antiquus (tom. cit. p. 116, pi. vi. fig. 2), from the Lower 
Burlington Limestone of Iowa; C. lircitus (tom. cit. p. 119, pi. vi. 
fig. 1), from the St. Louis Limestone of Illinois; C. springeri (tom. 
cit. p. 112, pi. vi. figs. 8-15), from the Upper Burlington Limestone 
of Iowa and Illinois; and C. tribulis (tom. cit. p. 117, pi. vii. 
figs. 18-21), from the Keokuk Limestone of Iowa and Illinois. 
Deltoclopsis (tom. cit. p. 158) is separated with hesitation from 
Deltodus , and also includes some deutal plates assignable to Sanda¬ 
lodus — e. g., the largfe “ upper v plate of S. morrisii. The following 
species are distinguished: D. ctffinis (tom. cit. p. 160, pi. xi. fig. 1), 
from the Warsaw Limestone of Illinois ; D. ? bialveatus (tom. cit. 
p. 169, pi. xi. fig. 15), from the Upper Burlington Limestone of 
Iowa; D. ? convexus (tom. cit. p. 169, pi. xi. figs. 17, 18), from the 
Upper Burlington Limestone of Iowa; D. ? convolutus (tom. cit. 
p. 165, pi. xi. figs. 11, 12), from the Upper Burlington Limestone 
