LAND ANIMALS OF THE COAL PERIOD. 365 



but implanted apparently in the same bones, there is a second series 

 of tcctli, 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 hollow 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 teeth appears in the skull 

 represented in Fig. 142, as the bones of the roof of the mouth have 

 been removed, adhering to the opposite side of the matrix. It will 

 be observed that all 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 towai'd 

 the front, and an inner series of larger and plicated teeth, as in the 

 upper jaw. 



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 four or five inches 

 in length, and is of massive proportions. The bones were hollow, 

 and in the case of the phalanges the bony walls were thin, so that 

 they are often found crushed flat. The humerus, howevei", 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. Fig. 142 shows the 

 humerus of the original specimen of the species. 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 indication of cartilaginous matter 

 lining it. 



The vertebrae, 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 centre. 

 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. Fig. 142 exhibits the usual form, and there 

 arc others with long spines above and below, reminding us of those 

 of the batrachians and reptiles which have tails flattened for swimming, 

 and probably indicating that this was the case with Dendrcrpeton. 

 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 



