In another nodule (No. 804, Yale Museum) there is a single bone preserved which resembles, to a great extent, a rib of the present species (fig. 15, E), although somewhat larger, and it has been provisionally identified as such. The element is very slightly curved, but shows the expanded head of the rib of this species. Measurements of the Type of Mazonerpeton costatum Moodie. No. 800 (777), Yale University Museum: mm. Length of portion of skull preserved 14 Length of right clavicle 16 Width of right clavicle 4 Length of dorsal region represented 30 Length of cervical rib 8 Length of dorsal rib 6-5 Length of caudal rib 3 Length of caudal portion of body preserved 55 Length of mandible 15 Greatest width 6 Length of right humerus 10 Greatest width of humerus 2 No. 804 (332), Yale University Museum: Length of rib 11 Width of head of rib 2 Diameter of shall 1 =Sparodus sp.= (?). Dawson, Phil. Trans. Roy. Sue. London, pt. II, p. 643, pl. 40, figs. 52 to 56, 1882. Dawson, Proc. and Trans. Roy. Soc. Canada, XII, p. 75. 195. Type: Specimen in the Peter Redpath Museum of McGill University. Horizon and locality: Coal formation at the South Joggins, Nova Scotia. The material on which the above determination is based was collected in 1878 by Sir J. W. Dawson in the coal formation at the South Joggins, Nova Scotia. Nothing has been collected since that date that would give additional information as to the nature of the form represented. I give here Dawson's description of the remains: "In the coaly matter or mineral charcoal at the base of tree No. 10 appeared a few fragments of an animal which may possibly belong to the above-named genus of Fritsch, though I am by no means certain of this identification or of the real nature of the animal. "The skull is represented by a fragment of a maxillary or intermaxillary bone, with blunt conical teeth. It is smooth or marked merely with microscopic dots. There is also a fragment which may be a palatal bone studded with minute teeth. "A few vertebræ associated with the above bones are long and narrow, with large zygapophyses and long neural spines. Length of body (i.e., of the vertebra) about 3 millimeters. "With these remains are a few bony scales different from those of any other species found in these trees, and more resembling scales of Ganoid Fishes. They are somewhat rectangular in form, enameled on the surface and beautifully sculptured with waving lines.