270 AIR-BREATHERS OF THE* COAL PERIOD. 



but in the mean time the very different form of the teeth is a 

 sufficient distinction. In IT. Lyelli these are conical and pointed. 

 In the present species they are of a peculiar wedge shape — their 

 diameter transversely to the jaw being the greatest at the base f 

 while at the top they are sharpened to an edge. The peculiar 

 form of the intermaxillary teeth may also serve as a distinctive 

 character, though those of H. Lyelli are not yet known. The 

 form of the vertebrae would further seem to indicate different pro- 

 portions of body. On the whole, while this species is in all pro- 

 bability generically related to the last, it is certainly specifically 

 distinct. Its habits and food may have been similar, but its den- 

 tal apparatus was stronger and more formidable. 



EXPLANATION OF PLATE VI, FIGS. 1 TO 16, AND FIG. 62. 



Hylonomus aciedentatus. 



Fig. 1 — Maxillary bone, magnified, (a) natural size. 

 " 2 — Mandible magnified, (a) natural size. 

 " 3 — Portion of mandible, natural size. 

 " 4 and 5 — Tooth, seen from the side and front. 

 " 6 — Tooth of intermaxillary. 

 " 1 — Cross section of tooth, magnified. 

 " 8 — Palatal bone with teeth. 

 " 9 — Frontal bone. 



" 10 and 11 — Rib natural size and cross section enlarged. 



" 12 — Pelvic bone. 



" 13 — Phalangial bone. 



" 14 and 15 — Bony scales magnified. 



" 16 — Broken vertebra. 



" 62 — Portion of skin with horny scales. 



IX. — Hylonomus Wtmawi. 



Plate VI, Figs. 18 to 31. 



This is the species of Hylonomus originally detected by Prof. 

 Wyman in the specimens brought from the Joggins by Sir C. 

 Lyell and myself. Remains of several additional individuals have 

 since been found, but no skeleton approaching to completeness. I 

 shall describe this the most diminutive of the reptiles of the Nova 

 Scotia coal, with the aid of the fragments represented in Plate 

 VI, Figs. 18 to 31, most of which are almost miscroscopic in size. 



