COCHLIODONIID^. 
217 
Dental plates differing from tkose of C. gibhus in the relatively 
less antero-posterior extension and the more rounded and prominent 
character of the coronal elevation. 
Form. ^ 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 ; Toredale llocks,\Vens- 
Icydale. Horne Coll. 
49634 . Pragmeut of dental plate ; Richmond. Purchased, 1878. 
According to the views of Agassiz, as interpreted by J. W. Davis, 
the so-called genera Sienopterodus, Chitonodus, and Deltodoptsis, 
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 oi Stenopiterodus" (lorn. cit. p. 100) might 
well be assigned to Beltodus and “ Streblodas.” They are described 
under the names of F. ehngatus {tom. cit. p. 106, pi. iv. figs. 1-3), 
from the Warsaw Limestone of lUiuois ; S. planus {tom. cit. p. 102, 
pi. iv. figs. 0-14), from tlie Upper Rurlingtoii Limestone of Iowa 
and Illinois ; and F. sp.‘? {tom. cit. p. 105, pi. iv. figs. 15, 16), from 
the Keokuk Limestone of Illinois. The tyiio species of Sandalodus 
(/S', parvulus, Newberry and Worthen) is also placed here. 
The dental plates of “ Chitonodus ” {tom. cit. p. 100) seem to bo 
assignable to Cochliodns, Beltodus, Poecilodus, and “ Streblodus,” 
and the genus is said (p. 112) to include Cochliodus latus, Leidy, 
Poecilodus rugosus, Newberry and Worthen, and P. ornalus, New- 
berry and Worthen. Four other species are distinguished as fol- 
lows : C. aniiquus (to»i. cit. x>. 116, pi. vi. fig. 2), from the Low'er 
Burlington Limestone of Iowa; C. liratus {tenn. cit. p. 110, pi. vi. 
fig. 1), from the St. Louis Limestone of Illinois ; C. springeri {tom. 
cit. p. 112, pi. vi. figs. 3-15), from the Upper Burlington Limestone 
of Iowa and Illinois; and 6’. tribidis {tom. cit. p. 117, pi. vii. 
figs. 18-21), from the Keokuk Limestone of Iow a and Illinois. 
Beltodopsis {tom. cit. p. 158) is separated with hesitation from 
Beltodus, and also includes some dental plates assignable to Sanda- 
lodus— e. g., the large “ upper ’’ x>latc of S. morrisii. The following 
species are distinguished: B. affinis {tom. cit. p. 160, pi. xi. fig. 1), 
from the Warsaw Limestone of Dlinois ; B.'l hialveatus {tom. cit. 
X). 169, pi. xi. fig. 15), from the Upper Burlington Limestone of 
Iowa ; B. ? convexus {tom. cit. p. 169, pi. xi. figs. 17, 18), from the 
Upper Burlington Limestone of Iowa ; B. ? convolutus {tom. cit. 
p. 16-5, pi. xi. figs. 11, 12), from the Upper Burlington Limestone 
