3GG THE CARBONIFEROUS SYSTEM. 



extremities are flattened and thin walled. The posterior limb seems 

 to have been not larger than the anterior, perhaps smaller. The bones 

 represented in Fig. 142, which I refer to this member, probably 

 belonged to a somewhat smaller individual than that to which the 

 humerus above mentioned belonged. The tibia is much flattened at 

 the extremity, as in some labyrinthodonts, and the foot must have 

 been broad, and probably suited for swimming 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 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 Arche- 

 gosaurus^ and also those oi Fholidogaster j)isciformis, recently described 

 by Huxley from the Edinburgh Coal-field, — an animal which indeed 

 appears in most respects to have a close affinity with Dendrerpeton. 

 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. 

 In one of the specimens the scales of the throat remain in their natural 

 position, and are seen to be of a narrow ovate fonn, and arranged in 

 imbricated rows diverging from the mesial line. 



This ancient inhabitant of the coal swamps of Nova Scotia was, in 

 short, as we often find to be the case with the earliest forms of life, 

 the possessor of powers and structures not usually, in the modern 

 world, combined in a single species. It was certainly not a fish, yet 

 its bony scales, and the form of its vertebrae and of its teeth might, 

 in the absence of other evidence, cause it to be mistaken for one. We 

 call it a batrachian, yet its dentition, the sculpturing of the bones of 

 its skull, which were certainly no more external plates than the similar 

 bones of a crocodile, its ribs, and the structure of its limbs, remind us 

 of the higher reptiles ; and we do not know that it ever possessed gills, 

 or passed through a larval or fish-like condition. Still, in a great 

 many important characters its structures are undoubtedly batrachian. 

 It stands, in short, in the same position with the Lepidodendra and 

 Sigillarice under whose shade it crept, which, though placed by pal^eo- 

 botanists in alliance with certain modern groups of plants, manifestly 

 differed from these in many of theii* characters, and occupied a different 

 position in nature. In the Coal period, the distinctions of physical 

 and vital conditions were not well defined — dry land and water, terres- 

 trial and aquatic plants and animals, and lower and higher forms of 

 animal and vegetable life, are consequently not easily separated from 

 each other. This is no doubt a state of things characteristic of the 

 earlier stages of the earth's history, yet not necessarily so ; for there 



