572 CARBONIFEROUS LABYRINTHODONT 
of the pectoral plates, so characteristic of all Labyrinthodonts, has 
made its appearance. They may possibly have been Amphibia; but 
their skulls, their cycloid scales, and their deeply biconcave, fish-like, 
vertebral centra appear to me to indicate a closer affinity with the 
Ophiomorpha (Cecilia, Ichthyophts, &c.) than with the Ladprin- 
thodontia. 
Of the unquestionable Labyrinthodonts which occur in the 
Carboniferous rocks, then, <l¢hracosaurus is the only genus regarding 
the vertebral column and ribs of which there is any information ; and 
the description and comparisons which I have given seem to me to 
necessitate the conclusion that, side by side with the Archegosaurian 
type, the Mastodonsaurian type of vertebral organization, hitherto 
known to occur only in the Trias,) was well developed in the 
Anthracosaurus of the Scotch coal-field. At the same time, the 
anchylosed condition of the neural arches, the supratemporal foramina 
Qvhich may, however, be parts of the ‘mucous grooves’ common upon 
Labyrinthodont skulls, the floor of which was very thin, or merely 
membranous in the temporal region of Axthracosaurius), and the 
strong median convexity of the snout, separate Axthracosaurus from 
any known Triassic Labyrinthodont. And though, in the general 
form of the cranium and in some other respects, Axthracosaurus has 
a certain resemblance to the Permian Dasyceps, it differs as widely as 
possible from it in its dentition. 
1 Nothing is at present known of the vertebree of Dasyceps Bucklandi, from the Bunter 
sandstein of this country. See Memoirs of the Geological Survey of Great Britain :—The 
Geology of the Warwickshire Coal-field ; by H. H. Howell, F.G.S. 1859. 
