272 AIR-BREATHERS OF THE COAL PERIOD. 



searched fur these among the vegetable debris of the coal swamps, 

 which would afford to a little creature like this abundant shelter. 

 It occasionally fell a prey to its larger reptilian contemporaries ; 

 for quantities of its tiny bones occur in coprolilic masses probably 

 attributable to Dendrerpeton. It is interest ng to find reptilian 

 life represented at this early period, not only by large and formi- 

 dable species, but by diminutive forms, comparable with the smal- 

 lest lizards and newts of the modern world. The fact is parallel 

 with that of the occurrence of several small mammalian species 

 in the mesozoic beds. It will be still more significant in this res- 

 pect if the species of Hylonomus should be found to be truly la- 

 certian rather than batrachian. 



EXPLANATION OF PLATE VI, FIGS. 18 TO 31. 

 Hylonomus Wymani. 



Fig. 18 — Lower jaw with teeth, magnified. 



" 19 — Anterior part of lower jaw more magnified. 



" 20 — Portion of maxillary bone with teeth, magnified. 



" 21 — Maxillary bone, natural size. 



" 22 — Lower jaw, natural size. 



" 23 — Vertebrae, natural size. 



" 24 and 25 — Vertebras, magnified. 



" 26 — Humerus, natural size and magnified. 



" 27 — Rib, natural size and magnified. 



" 28 — Pelvic bone, natural size and magnified. 



i " 29 — Foot ; the line shows the natural size. 



" 30 — Broken vertebra magnified, showing internal cavity. 



" 31 — Bony scales, natural size and magnified. 



X. — HvLERPETON DAWSONI. 

 Plate VI, Figs. 32 to 46. 



In the more or less laminated material which fills the interior 

 of the erect trees of the Joggins, it often happens that the more 

 distinctly separable surfaces are stained with ferruginous or coaly 

 matter, or with fine clay, so that the fossils which occur on these 

 surfaces, and which would otherwise be more available than those 

 in more compact material, are rendered so obscure as readily to 

 escape observation. This was unfortunately the case with one of 



