PETAIODOHIID^. 
61 
Type. Detached tooth ; (?) British Museum \ 
Single known species. 
Form. ^ hoc. Lower Carboniferous Limestone : Armagh. 
P. 2648-9. Specimens described and figured by J. W. Davis, loc. cit. 
Ennigkillen Coll. 
P. 2647, P. 2650. Four similar teeth. Ennukillen Coll. 
P. 2647 a. Naturally associated series of three teeth, showing the 
typical Petalodont arrangement. This specimen forms 
the basis of the description and figure by J. W. Davis, 
loc. cit. p. 511, pi. Isi. fig. 4. EnnisIciUen CoU. 
P. 1475. Imperfect tooth. Egerton Coll. 
Genus MESOLOPHODUS, nov. 
Teeth robust. Crown relatively thick, elevated, with a sharp 
cutting-edge ; posterior face of triangular outline, with truncated 
summit, slightly hollowed mesially, and with straight inferior 
margin ; anterior face of nearly similar form and size, but with a 
sharp vertical median ridge and W-shaped base-line. Base of 
crown with at least one largo fold. Hoot as deep as the crown, 
abruptly truncate. 
The supposed distinct genus represented by these teeth may 
perhaps pertain to the Petalodontidae. In some respects the teeth 
are suggestive of those named lAsgodw and Calopodus. 
Mesolophodus problematicus, sp. nov. 
Type. Detached teeth shown, nat. size, in PI. I. figs. 18, 19. 
Single known species. 
Form. Toe. Lower Carboniferous Limestone : Armagh. 
P. 2641. Type specimens. The original of PI. I. fig. 18 is a nearly 
complete crown displaying the anterior aspect. The 
tooth shown in PI. I. fig. 19 is nearly complete and ex- 
hibits the characters of the posterior aspect. 
Enniskillen CoU. 
P. 2641 a. Three abraded crowns. Enniskillen Coll. 
The so-called genus Cymatodus, H. Trautschold, 1879 {non New- 
berry and Worthen, 1870), may also probably be referred to the 
* An unmarked tooth in Admiral Jones's Collection, either in the Museum 
or in the possession of the Geological Society. 
