"Among the reptilian remains found in erect trees at the South Joggins, there have occurred several portions of skeletons which, from their sculptural cranial bones, plicated teeth, and the forms of their scales and limb-bones, I have referred to the genus _Dendrerpeton_, but to individuals of much smaller size than the full-grown specimens of _D. acadianum_. It did not occur to me to suppose that these were specifically distinct from the larger individuals, until I observed that bones of this kind, contained in the collections sent by me to the Geological Society, or represented in the figures drawn to illustrate one of my papers, were referred by Professor Owen, in his notes on these specimens and figures, in the Journal of the Geological Society, to the genus _Hylonomus_; which is quite distinct from _Dendrerpeton_, as will be explained in sequel. "I was thus induced to reexamine all the specimens in my collection and the result has been to establish a strong probability that there is in reality a second species of Dendrerpeton, smaller than _D. acadianum_, and differing from it in several points. This species I propose to name _D. oweni_. It differs from _D. acadianum_ in the following particulars: (i) its much smaller size; (2) its long and hooked teeth (it will be seen that these teeth differ very markedly in their proportions and form from those of the larger species);(3) the greater plication of the ivory in the intermaxillary teeth (in _D. acadianum_ these teeth are, on the outside, simple almost to the base, and plicated on the inner side, while in this species they are plicated all around like the inner maxillary teeth);(4) the form of the skull, which has the orbits larger in proportion, and is also shorter and broader. On the other hand, when we have described the species Hylonomus, it will be seen that this animal, except in size, differs from them quite as widely as does _D. acadianum_. "The distinctness of _D. oweni_ is further confirmed by the fact that I possess small jaw-bones of _Dendrerpeton_, about the size of those of this species, but having the teeth similar in form to those of the larger species; these I suppose to have belonged to young individuals.