276 Messrs. Hancock & Atthey on Reptile- and Fish-Remains 
external nostrils, and the difference in the form of the cranial 
bones, as well as the smallness and different character of the 
teeth of that genus, sufficiently distinguish it from Pteroplax. 
This new genus is also related to Antienéosaele as 18 ap- 
parent by the similarity of the vertebree, the only difference of 
importance being that in this new Labyrinthodont there is a 
minute notochord, while the centrum of Anthracosaurus is 
completely ossified, and the neural arch of the former is oval 
instead of being triangular as it is in the latter. The 
occipital region, also, in the two forms is very different. And, 
the teeth disagree both in form and minute structure ; indeed, 
the strongly compressed crown, with its wide cutting-edges, 
seems very characteristic in Pteroplax cornuta. 
When the tooth is seen in transverse’ section, converging 
spaces are observed dividing the internal vertical folds or 
plice of dentine ; these spaces are widest towards the periphery 
of the tooth, and are nearly all lost before they reach the pulp- 
cavity, the plicee having coalesced at their internal extremities*. 
The plice are much undulated or lobulated, and have, extending 
through the centre in a radial direction, a double line of gra- 
nular matter, divided by a thin, clear, homogeneous substance. 
This compound line takes an undulatory or zigzag course, 
and sends a simple process from each angle into the lateral 
lobes or undulations.. The two granular lines are continuous 
with a similar line that follows the sinuosities of the peripheral 
dentine; and the clear layer between these granular lines ap- 
pears to be continuous with the clear coating of the tooth 
which would seem to be composed of cement, the enamel pro- 
bably not extending to the base of the tooth. The Laby- 
rinthodont structure of the tooth would therefore appear to 
formed by the vertical infolding or plication of the Fen grine 
wall of dentine and its external coating. It is evident, then, 
that the minute structure of the tooth of Pteroplax differs 
considerably from that of Anthracosaurus, in which, according 
to Prof. Huxley, the radiating plice are not formed in this 
way. 
4 Ophiderpeton nanum, n. sp. 
A single individual of a curious serpent-like Labyrinthodont, 
which apparently belongs to this genus, has been found at 
Newsham. It is not, however, in a good state of preservation, 
though the characters are sufficiently distinct to permit of the 
* Since the above was in print we have examined other sections of the 
tooth, and find that the radial spaces dividing the plice of dentine are 
occasionally continuous with the pulp-cavity ; it would therefore seem 
that in the minute structure the tooth differs less from that of Anthraco- 
saurus than we supposed. 
