Description of Specimens of Fossil Reptilla discovered in the Coal-measures of the South Joggins, Nova Scotia, by Dr. J. W. Dawson, F.G.S., &c.

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Abstract
The following specimens were transmitted to the Museum of the Geological Society by Dr. Dawson, in a series of boxes and parcels, most of which are numbered according to a list accompanying them, and have been submitted, by his desire, to my inspection. The descriptions will follow in the order of that list. “Box No. 1.— Hylonomus Lyelli , Dawson.„ This specimen is imbedded in a portion of a thin layer of carbonaceous matter, measuring six inches by four inches. It consists of scattered parts and impressions ofvertebrm, ribs, limb-bones, and part of a cranium crushed, including part of a maxillary bone with teeth (P1. IX. figs. 1-5). Not any of the bones are entire: all the long bones, even the ribs, are hollow; and the cavity is enclosed by a compact wall of almost uniform thinness throughout each bone, indicative that such cavity was not properly a medullary one, in the sense of having been excavated by absorption after complete consolidation of the bone by the ossifying process, but was posthumous, and due to the solution of the primitive cartilaginous mould of the bone, which had remained unchanged by ossification in the living species. I conclude, therefore, that these hollow long bones (and, indeed, the bodies of the vertebrm seem only to have received a partial and superficial crust of bone) were originally solid, and composed, like the bones in most Batrachia, especially the Perennibranehlates, of an external osseous crust, enclosing solid cartilage. The body of the vertebra (figs. 1

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