[Illustration: MOODIE PLATE 10 _Hylonomus latidens_ Dawson. Skull, portion of skeleton, foot, scapula, sternal bones, humerus, and rib, believed to belong to this species. Erect tree, Coal formation. Nova Scotia. Nearly natural size. Photograph by Dawson, published through the courtesy of Dr. Arthur Willey. Original in the Peter Redpath Museum of McGill University.] mm. Length of skull 8 Length of mandible 5 Length of rib 5.5 Length of femur 6 Length of humerus 5 =Genus SMILERPETON Dawson.= Dawson, Phil. Trans. Roy. Soc., London, 1882, pt. H, p. 634. Dawson, Proc. and Trans. Roy. Soc. Canada, 1895, p. 74. Type: Smilerpeton aciedentatum Dawson. The type species was originally referred to _Hylonomus_, but further study induced Dawson to refer it to a new genus. Dawson gives (216) the following characteristics 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, _S. aciedentatum_, from the Coal Measures at the South Joggins, Nova Scotia." =Smilerpeton aciedentatum Dawson.= Dawson, Quart. Jour. Geol. Soc. London, XVI, p. 275, figs. 19 to 23, 1860. Dawson. Air-breathers of the Coal Period, p. 65, 1863. Dawson, Phil. Trans. Roy. Soc. London, 1882, pt. II, 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 vertebræ 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.