THE MICROSAURIAN FAMILY HYLONOMID^. 8 1 



brae of this species were found partially associated, indicating a long, slender body. 

 The body is covered with scales and ventral scutellae are present. Dawson ques- 

 tions whether this species may not be the young of H. lyelli. 



mm. mm. 



Length of skull 8 Length of femur 6 



Length of mandible 5 Length of humerus 5 



Length of rib 5.5 



Genus SMILERPETON Dawson. 



Dawson, Phil. Trans. Roy. See, London, 1882, pt. 11, p. 634. 

 Dawson, Proc. and Trans. Roy. Soc. Canada, 1895, p. 74. 



Type: Smilerpeton aciedentatum Dawson. 



The type species was originally referred to Ilylonomus, but further study induced 

 Dawson to refer it to a new genus. Dawson gives (216) the following character- 

 istics of the genus: 



"Form somewhat elongated, and limbs short. Mandibular and maxillary teeth wedge- 

 shaped, with cutting edges. Palatal teeth numerous, some of them large. Abdominal 

 scales oval. A single species is known, 5. aciedentatum, from the Coal Measures at the South 

 Joggins, Nova Scotia." 



Smilerpeton aciedentattun Dawson. 



Dawson, Quart. Jour. Geol. Soc. London, xvi, p. 275, figs. 19 to 23, i860. 



Dawson. Air-breathers of the Coal Period, p. 65, 1863. 



Dawson, Phil. Trans. Roy. Soc. London, 1882, pt. 11, p. 638, plate 40, figs. 28 to 45. 



Dawson, Proc. and Trans. Roy. Soc. Canada, 1895, p. 75. 



Dawson, Acadian Geology, 3d ed., p. 376. 



Type: Specimen No. 3061-3, Peter Redpath Museum, McGill University. The 

 British Museum (393, pt. iv, p. 224) also has a specimen, No. R 433. 



The important characteristic (plate 12) is found in the form of the mandibular 

 and maxillary teeth, which are of a peculiar wedge-shape, being broad and oval 

 at the base and narrowed to a longitudinal edge at top. Thus, when viewed from the 

 side they appear narrow and blunt, but when the jaw is broken across, and they are 

 viewed from the rear or front, they appear broad and sharp-edged. The effect of 

 this arrangement is that the jaw is armed with a closely placed series of chisels or 

 wedges, giving an almost continuous edge. At the end of the mandible some of the 

 teeth are longer and more conical. 



Another important character is that the palatal and vomerine bones seem to 

 have bristled with teeth, mostly of very small size; but there are also some larger 

 palatal teeth, of which some are sharply pointed and others blunt with furrowed 

 points. 



The vertebrae are of the same type as those of Hylonomus; but some which appear 

 to be caudal have a pointed spine above, indicating perhaps a flattened tail. The 

 ribs are short and stout. 



The body seems to have possessed an interclavicle and ventral scutellae. Above 

 it was, apparently, clothed with small tubercles and homy scales, and to have had 

 cuticular pendants like those of Dendrerpeton. 



