452 On the Fossil Fishes of the Carboniferous Iimestone Series of Great Britain. 
marked with two strong, revolving ridges, separated by a deep furrow, which 
correspond to the larger of the two teeth of either ramus of the jaw, figured by 
Prof. Agassiz (‘ Poiss. Foss. Atlas,’ Vol. IIL, tab. 19, fig. 14), constituting the 
type of the genus Cochliodus, and the tooth described by Prof. M‘Coy under the 
name of C. acutus, Ag. (‘ Brit. Paleeoz. Foss.,’ p. 621, Pl. 3 I, figs. 24, 25). The 
differences between these teeth and ours being only of a specific character, 
2nd. A narrow tooth equally convoluted, and having a wedge-shaped outline 
when seen from above, perhaps corresponding to the anterior pair in Agassiz’s 
figure. This tooth has a single narrow and low revolving ridge, with numerous 
obscure plications. 3rd. Teeth nearly as long as both the preceding. These teeth 
are somewhat unlike any hitherto attributed to Cochliodus, and probably belenged 
to the opposite jaw from that which bore those before mentioned ; matching into 
those when in use. If the teeth described by Agassiz and M‘Coy are, as supposed, 
from the lower jaw, these are from the upper. 4th. Transversely elongated teeth 
of smaller size, in diminishing series of size, joined by their longer sides, and in 
some cases retaining their relative positions, These teeth have a more or less 
distinctly marked prominence or cone upon the crown, and an oblique and flattened 
root often as high as the crown, Considered by themselves, they would constitute 
one or more typical species of Helodus, 
“They formed several rows, as is indicated by the differences which they present. 
The enamelled surface of all these teeth, large and small, has a relatively 
coarse porosity, precisely the same in all, and it is impossible to resist the conclusion 
that they all formed parts of the varied dentition of a single fish. As they are 
now thrown into a confused heap we can only conjecture what the relative position 
of each form was. It seems probable, however, that the smaller conical teeth 
(Helodi) formed several series intermediate between the larger and broader ones, 
upon the symphysis of the jaw. In the living Cestracion we find a precisely similar 
arrangement. The rami of the jaws are covered with a series of broad, flattened 
plates, fitted for crushing only, while the mesial portion of each jaw is occupied by 
numerous rows of small pointed teeth, diminishing in size from front to rear.” 
Whether the median teeth in the fossil Helodus (Cochliodus) were on a single row 
or were common to both, Mr. Worthen was unable to determine. The specimens. 
were named Helodus (Cochliodus) nobilis, (N. and W.) 
If the observations recorded above are correct, and there appears little doubt that 
they are, the teeth, hitherto considered as distinct genera, are proved to belong to 
fishes which had a somewhat complicated dentition, and a thorough revision of the 
whole of the palatal forms of teeth may eventually be necessary. At present, 
however, the grounds are so slight on which to raise such a fabric that it is im- 
possible to more than hint at such a result, and to hope that ere long fresh dis- 
coveries may serve to elucidate the true organization of the fishes that gave origin 
to the fragmentary remains, which are all we now possess. In the fossil Helodi, 
found in the Carboniferous rocks in Britain, there is little evidence to show either 
