THE TEMNOSPONDYLOUS AMPHIBIA. 



portion ; and much resembles that of the labyrinthodont reptiles of the Trias. The bones 

 of the skull are sculptured as in Baphctcs, but in a smaller pattern. The nostrils are small, 

 and near the muzzle; the orbits are circular, and separated by a space of more than their 

 own diameter. In the upper jaw there is a series of conical teeth on the maxillary and inter- 

 maxillary bones. Those on the intermaxillaries are much larger than the others, and have 

 the aspect of canines or tusks. Within this outer series of teeth, but implanted apparently 

 in the same bones, there is as in Archc^saunis a second series of teeth, closely placed, or 

 with intervals equal to the diameter of one tooth. These inner teeth are longer than the 

 others, implanted in shallow sockets, to which they are anchylosed, and have the dentine 

 plicated, except toward the point. A third group of teeth, blunt at the points, largely hol- 

 low in the interior, and with the dentine quite simple, appears in detached bones, which 

 may represent the vomer. Only a part of this formidable armature of the teeth appears in 

 the skull, as the bones of the roof of the mouth have been removed, adhering to the opposite 

 side of the matrix ; but the fact of the occurrence of two sets of teeth was ascertained by 

 Professor Wyman, from the original specimens, and is manifest in the fragment : 

 while the other teeth, supposed to be vomerine, appear in fragments which must, from their 

 size and collocation, have belonged to DcnJia'pctou. It will be observed that all of these 

 teeth are anchylosed to the bone ; and that those of the vomer are thinly walled and simple, 

 the outer series on the maxillaries and intermaxillaries simple and flattened, while the inner 

 series of teeth are conical and plicated. In the lower jaw there was a uniform series of 

 conical teeth, not perceptibly enlarged toward the front ; at least this is the case in the only 

 specimen at present in my collection; which is, however, merely an imperfect cast in 

 hard sandstone. 



' ' The scapular and sternal bones seem to have been well developed and strong, but only 

 portions of them are known. The fore limb of the adult animal, including the toes, must 

 have been 4 or 5 inches in length, and is of massive proportions. The bones are hollow, and 

 in the case of the phalanges the bony walls were thin, so that they are often found crushed 

 flat. The humerus, however, was a strong bone, with thick walls and a cancellated structure 

 toward its extremities; still, even these have sometimes yielded to the great pressure to 

 which they have been subjected. The cavity of the interior of the limb-bones is usually 

 filled with calc-spar stained with organic matter, but showing no structure ; and the inner 

 side of the bony wall is smooth, without any indications of cartilaginous matter lining it. 



"The vertebra;, in the external aspect of their bodies, remind one of those of fishes, 

 expanding toward the extremities, and being deeply hollowed by conical cavities, which 

 appear even to meet in the center. There is, however, a large and flattened neural spine. 

 The vertebrae are usually much crushed, and it is almost impossible to disengage them from 

 the stone. * * * in its long neural and hasmal spines, reminds us of the caudal vertebras of 

 those batrachians and reptiles which have tails flattened for swimming, and probably indi- 

 cates that this was the case with Dendrerpeton. The ribs are long and curved, with an 

 expanded head, near to which they are solid, but become hollow toward the middle ; and the 

 distal extremities are flattened and thin- walled. The posterior seems to have been not 

 larger than the anterior, perhaps smaller. The tibia is much flattened at the extremity, as 

 in some labyrinthodonts, and the foot must have been broad, and probably suited for swim- 

 ming or walking on soft mud, or both. That the hind limb was adapted for walking is shown 

 not merely by the form of the bones, but also by that of the pelvis, the best preserved speci- 

 men of w r hich I have represented (208, pi. in, fig. 28). 



"The external scales are thin, oblique-rhomboidal or elongated-oval, marked with 

 slight concentric lines, but otherwise smooth, and having a thickened ridge or margin ; in 

 which they resemble those of Archegosaurus, and also those of PlioliJo&istcr. '' ' The 

 microscopic structure of the scales is quite similar to that of the other bones, and different 

 from that of the scales of ganoid fishes * * * ." 



