I. AND ANIMALS OF THE COAL PERIOD. .".T'.l 



in the lower jaw, and they are alternately large and small, aa if replaced 

 in this manner as worn <>ut. Their structure is of the same simple 

 character as in the other species of Hylonomus, and they have large 

 pulp cavities. 



The vertebra' of this species arc singular and characteristic. The 

 bodies are elongated and hour-glass shaped, with an internal cavity 

 of the same form tilled with calc-spar, and probably once occupied by 

 cartilage. They have, in the dorsal region at least, strong articulating 

 and lateral processes, and were furnished with numerous delicate ribs. 

 In one of my specimens as many as thirty-eight of these little vertebra 

 may be seen lying together, and many of them attached to each other. 

 This would indicate that the body was long and slender. It was 

 furnished with limbs similar to those of H. Lyrtli, but of course, 

 smaller. The pelvis is of the same expanded form with that of the 

 last species, and a pair of fore-feet lying together on one slab show 

 the remains of four slender toes. The bones of the limbs are very 

 delicate and thin-walled. The bony scales are oval, and similar to 

 those of the other species of the genus, but very small. 



In length, Hylonomus Wymani could not have exceeded four or 

 five inches, including the tail. It may indeed be questioned whether 

 this little creature was not the young of one of the other species. 

 The form of the vertebra? and teeth would, however, prevent us 

 from supposing that it stood in this relation to II. Lyelli. To H. 

 acirdentatus it bears a stronger resemblance in these respects, though 

 not sufficient to render specific identity probable ; and the occurrence 

 of so many specimens of the smaller species, without any of inter- 

 mediate size, renders it likely that it did not attain to any greater 

 dimensions. 



Hylonomus Wymani probably fed on insects and larva?, and searched 

 for these among the vegetable debris of the coal swamps, which would 

 afford to a little creature like this abundant shelter. It occasionally 

 fell a prey to its larger reptilian contemporaries ; for quantities of its 

 tiny bones occur in coprolitic masses, probably attributable to Den- 

 drerpeton. It is interesting to find reptilian life represented at this 

 early period, not only by large and -formidable species, but by diminu- 

 tive forms, comparable with the smallest lizards and newts of the 

 modern world. The fact is parallel with that of the occurrence of 

 '■lal small mammalian species in the mesozoic beds. It will be 

 still more significant in this respect if the species of Hylonomus should 

 be found to be truly laccrtian rather than batrachian. 



