376 Messrs. Hancock & Atthey on Reptile- and Fish-Remains 
structure ; but such specimens are mounted in balsam, which, 
we have seen, is liable to render minute structure invisible. 
It is therefore not improbable that the specimens of M. 
Agassiz may have been mounted in this medium; and it is 
equally likely that the minute structure was not preserved in 
the fossil examined by him. Such discrepancies must be ex- 
pected in the examination of fossdls; and accordingly we have 
already seen that the minute structure in Ctenodus had escaped 
the observation of that naturalist. | 
In Ageleodus we see another striking instance of the danger 
of trusting entirely to the sections of objects not previousl 
understood. From this cause the denticles are described as if 
their whole contour was seen, whereas there is nothing but 
the mere stumps left in the section, the crowns all having been 
cut away in making it. As the denticles are (as we have 
already stated) recurved, they must necessarily, to a great ex- 
tent, be removed in such a section as that figured. ‘Had this 
been previously known, the bases of the denticles could never 
have been mistaken for their crowns, nor could the latter have 
ever been described as “broader than they are high;’ nor 
could it have been stated that they all “terminate obtusely ; 
and this seems to be an original form, not due to wear or 
abrasion.” In fact, Prof. Owen describes merely a diagonal 
section of the basal portion, and supposes that he describes the 
whole denticle. This author has likewise been deceived into 
the belief of the existence of a common pulp-cavity, by the 
removal in the section of the osteo-dentine near the centre of 
the specimen. Here all the substance has been ground awa 
in consequence of the lateral sigmoid bend before destined: 
A lateral section proves that no such cavity exists; and, in- 
deed, the large series of sections now before us, and which 
were made many years ago, entirely disprove this assertion. 
The inference drawn from the supposed presence of this cavity 
is therefore of no avail. 
We have now examined the whole of the new genera and 
species of Fishes and Batrachians proposed by Prof. Owen in 
his paper published in the ‘ Transactions of the Odontological 
Society,” and find ourselves compelled to conclude that there 
is positively not a single novelty in the whole series. Thirteen 
genera were enumerated in the ‘“ Abstract” of the paper as 
read; in the paper as published there are only twelve, one 
(entitled ‘‘ Oreodus’’) having been withdrawn. It is unfor- 
tunate that some circumspection had not been also observed 
with regard to the remaining twelve, which, we fear, are fated 
to fall into the like obscurity. We have found as we 
approached the ‘‘ New Coal Fishlets’’ that they gradually 
