82 Mr. T. Atthey on various Species of Ctenodus 
ribs cannot have belonged to any of the other large species of 
our coal-system, as none of them have, so far as known, ossi- 
fied ribs ; neither can they be assigned to Campylopleuron, a 
new genus recently proposed by Prof. Huxley* for some large 
coal-measure fishes found in Ireland, which have not only 
ossified ribs, but have also large opercula. These opercula, 
however, being “ characterized by a raised longitudinal rib,” 
differ from those of Ctenodus, which have no such process or 
gee ae 
All the tooth-plates described in the sequel of this commu- 
nication have such a general resemblance to each other that . 
there can be no doubt of the close relationship of the fishes to 
which they belong. And, moreover, the bones to which many 
of them are found attached closely resemble each other. The 
palatal tooth (or that which has been so designated) is seated 
on a broadish flattened bone which, with one exception, is 
never more than twice the length of the tooth, and is usually 
considerably shorter; and it is always much expanded at the 
posterior extremity. This is probably a maxillary bone; and 
the two branches, when united, have much the appearance of 
an upper jaw. ‘I'he propriety, therefore, of calling these pa- 
latal plates or teeth may be questioned. The homologies, 
however, of these parts must be left for the present untouchedy. 
The mandibular tooth is always much narrower than the pa- 
latal, and the branch of the mandibulum on which it is placed 
is not so wide as the bone supporting the palatal tooth, neither 
is it so much expanded at the posterior end; it is, however, 
strong and rather massive. 
There are two species that have the surface of the teeth 
with smooth ridges, not tuberculated or denticulated as they 
are in all the other kinds. These two have consequently 
some resemblance to the palatal plates of Ceratodus, apparently 
a closely allied form. When further research shall have 
thrown more light on these obscure species, it will then be 
time enough to consider the desirableness of dividing this appa- 
rently natural group into separate genera, 
I shall now Bands this brief communication with concise 
descriptions of the various dental plates that have come under 
my observation, retaining the denomination of palatal plates 
or teeth for the upper pair, though the bones to which they 
are attached have all the appearance of maxillaries, and so 
they will be named in the following descriptions. 
* Geol. Mag. vol. iii. p. 166. 
+ This matter is undoubtedly discussed in Prof. Pander’s ‘Monograph 
on the Ctenododipterini ;’ but I have not seen that important work. 
