420 On the Fossil Fishes of the Carboniferous Limestone Series of Great Brita. 
dentition of the two groups no doubt indicates a difference in the food of the fishes. 
The sharp teeth in front and the crushing teeth behind, are well adapted for seizing 
and crushing hard-shelled animals, such as crustaceans or molluscs, which probably 
served as their food, whilst that of the Cochliodonts, from the flat or rounded 
dentition, without, so far as is known, any sharp teeth for seizing animals of any 
kind, leads to the inference that they were in the main, vegetable feeders. 
It has been already shown that the teeth of Orodus, Agassizodus, and other 
allied genera bear a very close resemblance to the existing Cestracion, only diverg- 
ing in one or two minor points. These forms, found along with the Cochliodonts 
in the Mountain Limestone, are so completely separated by their difference in form, 
arrangement, and adaptations to the feeding of the fish, that they afford strong 
evidence against their being members of the same group. The teeth of the living 
Cestracion and those of the fossil Agassizodus, &c., are arranged on the rami of the 
jaws without any intermediate palates or teeth; the dental arrangements of 
Cochliodus, of Psephodus, and doubtless of others, combines the lateral teeth 
enveloping the jaws along with other teeth which extend across the entire palate, 
and the gape was without doubt much wider in the latter group. These differences 
serve to separate the Cochliodonts from the Cestraciont sharks, whilst at the same 
time, it cannot be denied, as indicated by Professor Agassiz, that there is a somewhat 
close relationship between the dentary apparatus of this group and that of the 
Ceratodi. 
Genus—Cochliodus, L. Agassiz, 1838. 
Syn. Psammodus, (pars.) 1833. L. Agassiz. 
Teeth, medium size, two or perhaps three teeth to each ramus of the jaw, 
remarkable for their enrolled and twisted form and the obtuse angle formed by 
the rami of the jaws in front. Anterior teeth small, triangular, deeply convoluted ; 
posterior teeth larger, more or less oblong in outline, with three ridges arranged 
radially from the inside of the tooth outwards, surface smooth, finely punctate 
Base : concave, osseous, smooth. 
