| OCR Text |
Show 1869.] MR. ST. GEORGE MIVART ON ANUROUS BATRACHIANS. 281 it adopts from the labours of Mr. Cope osteological characters noticed by him, but which are here restricted in their application to the limitation of more subordinate groups than those for which he uses them. Mr. Cope's osteological system would divide the Anura into two great series, the Arciformia and the Raniformia. The Raniformia are thus characterized * : - " Coracoidei abutting ; epicoracoidei, when present, continuous, transverse, and abutting on coracoidei; not connected with the latter by overlapping longitudinal cartilages." The Arciformia are distinguished as follows f : - " Acromials and coracoids divergent, the former directed forward and connected with the latter by a longitudinal arched cartilage, which is free from, and overlapped by, the corresponding cartilaginous arch of the opposite side." This system associates Bombinator, Pelodytes, and Cultripes with Hyla, Cystignathus, Hylodes, and Bufo, in one division; while Engystoma, Phryniscus, and Hemisus are altogether separated from the true Toads, in order to be classed with Rana, Hylarana, &c. Such approximations seem to m e forced and unnatural, and likely to lead to the rejection of the system from which they necessarily result. Mr. Cope employs other osteological characters for more subordinate groups; thus his Hylidce% are characterized, among other points, as having the " fronto-parietalia shortened anteriorly, usually embracing a fontanelle," and " superior plate of ethmoid never covered by fronto-parietals, usually produced anteriorly, between fronto-nasals." Skeletal characters are, indeed, most valuable ones in leading us to detect the deepest and truest affinities of vertebrate animals. But these affinities once found/it is very desirable that zoological classifications should not, if it can possibly be avoided, repose upon them only, but rather on more external and more readily ascertainable characters. Such external characters will probably be found to exist in all really natural groups, although thev may turn out to be distinctions so little obvious that they might never have been noticed, but for the guidance afforded by the previous careful study of the osteology of such groups. As to the particular character selected to distinguish Mr. Cope's two great primary divisions, I cannot think it of anything like the importance § he attaches to it. The point is one easily to be studied, as the Common Frog is the type of the Raniformia, while the Common Toad exemplifies the Arciform type of structure. When the two adult shoulder-girdles are compared, a considerable * Journal Acad. Phil, new series, vol. vi. pt. 2, p. 190. t Ibid. pt. 1, p. 67. j Ibid. p. 83. § I a m fortified in this, I rejoice to say, by the valuable opinion of one of the very first of existing osteologists, I mean m y esteemed friend Mr. W . K. Parker, F.R.S. |
