COCHLIODONTID®. 
191 
{ihid. p. 88, pi. iv. fig. 20), V. (?) hpis, St. J. & W. {ibid. p. 88, 
pi. iv. fig. 21), V. {!) similis, St. J. & W. {ibid. p. 86, pi. iv. 
figs. 17-19), and V.(!) simplex, St. J. &,W. (ibid. p. 84, pi. iv. 
figs. 22-26). The last-named “species” comprises a triangular 
tooth. 
Closely related to Saiidalodus is the genus and species Platyodm 
lineatus, J. S. Newberry (Eep. Geol. Surv. Ohio, vol. ii. pt. ii. (1875), 
p. 58, pi. lix. fig. 12), founded upon a tooth from the Waverly 
Shales of Kentucky. 
Genus TOMODUS, Davis (ex Agassiz, MS.). 
[Trans. Eoy. Dublin Soc. [2] vol. L 1883, p. 446.] 
Dental plates thick, massive, triangular in outline, gently arched, 
and the outer apex stronglj' inrolled ; coronal surface smooth, 
punctate. One lateral margin — apparently the antero-lateral — 
straight, presenting an abrupt face with a sharp angulation above ; 
the crown at the opposite margin becoming thinner, with an 
extension of the root beyond ; inner margin gently curved, making 
a right angle with the antero-lateral margin. 
Before the definition of this “ genus,” the name Tomodus had 
already been proposed by Trautschold ' for a narrow high-crowned 
tooth from the Carboniferous Limestone of Eussia (see p. 229). Since, 
however, the term is in each case provisional, and as Trautschold 
has more recently “ renamed the Eussian tooth Oxyiomodm, it does 
not appear advisable to alter the accepted name of the teeth described 
below. 
Tomodus convexus, Davis. 
1838. Cochliodus contortus, L. Agassiz (in part), Poiss. Foss. vol. iii. 
p. llo, pi. xiv. figs. 23-25. 
1862. Tomodus conve-xus, Morris & Koberts (ex Agassiz, MS.), Quart. 
Journ. Geol. Soc. vol. xviii. p. 101 (name only). 
1883. Tomodus convexus, J. W. Davis, Trans. Eoy. Dublin Soc. [2] 
vol. i. p. 446, pi. Iv. figs. 15-18. 
1883. Tomodus convexus, St. John k Worthen, Pal. Illinois, vol. vii. 
p. 172. 
Type. Detached dental plates ; Bristol Museum. 
The type species. Dental plates (according to Davis) of two 
kinds, larger and smaller. The large plate convex in each direction, 
the coronal surface without ridges and furrows ; maximum distance 
1 If OUT. M^m. Soc. Imp. Nat. Moseou, toI. xiv. (1879), p. 65. 
’ Bull. Soo. Imp. Nat. Moseou, 1880, pt. ii. 
