2/4 THE OLDEST AIR-BREATHERS 



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. The 

 ribs are long and curved, showing a reptilian style of chest. 

 The posterior limb seems to have been not larger than the 

 anterior, perhaps smaller. The tibia, or principal bone of the 

 fore leg is much flattened at the extremity, as in some Labyrin- 

 thodonts, 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 elon- 

 gated-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 Pholi- 

 dogaster pisciformis, described by Huxley from the Edinburgh 

 coal field, an animal which indeed apppears 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, the 

 shape of the cells being batrachian. For other particulars of 

 its structure reference may be made to the papers named at 

 the end of the chapter. 



With respect to the affinities of the creature, I think it is 

 obvious that it is most nearly related to the group of Labyrin- 

 thodonts, and that it has the same singular mixture of batra- 

 chian and reptilian characters which distinguish these ancient 

 animals, and which give them the appearance of prototypes of 

 the reptilian class. A second and smaller species of Den- 

 drerpeton was subsequently obtained at the Joggins, and others 

 have been found, more especially by Fritsch, in the Carboni- 

 ferous and Permian of Europe. 



This ancient inhabitant of the coal swamps of Nova Scotia 



