276 Messrs. Hancock & Attliey on Reptile- and Fish-Remains 



external nostrils, and tlie 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 Anthracosaurus, as is ap- 

 parent by the similarity of the vertebra?, 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 

 plicae of dentine ; these spaces are widest towards the periphery 

 of the tooth, and are nearly all lost before they reach the pulp- 

 cavity, the plic£e having coalesced at their internal extremities*. 

 The plica3 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 be 

 formed by the vertical infolding or plication of the peripheral 

 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 Anth-acosaurus, in which, according 

 to Prof. Huxley, the radiating plicse are not formed in this 

 way. 



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 a"bove was in print we have examined other sections of the 

 tooth, and find that the radial spaces dividing the plicae 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. 



