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Show 1888.] CLASSIFICATION O F T H E RANIUJE. 205 number of species they may embrace ; by so doing he firstly facilitates identification, for the student has a right to expect, when using a synoptic work, to get at the name of the genus before that of the species; and secondly, he more correctly expresses the continuity and breaks in the series of forms as exist in Nature at the present period. This mode of treatment has therefore both a practical and a philosophical bearing. M y arrangement has not met with general acceptance. As for myself, I have not lost sight of the question during the six years that have elapsed since the publication of my classification, and I have, on different occasions, taken up the matter again in the hope of finding characters upon which to subdivide the genus Rana, but without success ; and I am now more than ever convinced that it is a natural association. This conviction has been confirmed by a discovery published by Peters (Reisen. Mossamb. iii. 1882), shortly after the issue of the Brit;sh Museum Catalogue. He found that the digits of most of bis Polypedatince differ from those of the Ranince by the presence of a small additional phalanx between the uhimate and what is normally the penultimate; the number of phalanges being 3, 3, 4, 4 in the fore limb, and 3, 3, 4, 5, 4 in the hind limb, instead of 2, 2, 3, 3 and 2, 2, 3, 4, 3. After testing the constancy of this character, I fully endorse Peters's view as to its taxonomic importance ; it affords a far better character for separating Rhacophorus from Rana than does the presence of a web between the fingers. And I find, with satisfaction, that all the species referred by me, from autoptic examination, to the genus Rana have the normal phalanges, irrespective of the presence or absence or size of the digital expansions. Two species which were formerly unknown to me, but of which specimens are now in the Museum, viz. Hyla bucrgeri, Schleg., and Theloderma leprosum, Tsch. ( = Polypedates leprosus, Gthr.), must, in spite of their free fingers, be referred to Rhacophorus. I also find that Cassina, though oxydactyle, and therefore placed by Peters in his Raninae, has the additional phalanx like its close ally Hylambates ; and that the genus Ixalus, as hitherto defined, is unnatural, the species opisthorhodus, Gthr., silvaticus, Blgr., fuscus, Blgr., saxicola, Jerd., and doubtless also sarasinorum, F. Mull., all from Southern India and Ceylon, standing in the same relation to Rana as the typical Ixali to Rhacophorus. For these species, characterized by the normal number of phalanges, I propose the generic name Micrixalus. Considering the importance of the character discovered by Peters, I would suggest the division of the Ranidce into two groups, that which is characterized by the additional phalanx embracing the following genera :- Cassina, Gir., Hylambates, A. Dum., Rappia, Gthr., Megalixa-lus, Gthr., Rhacophorus, Kuhl, Chiromantis, Ptrs., Ixalus, Tsch., and Nyctixalus, Blgr. The following figures show that the character upon which these two groups are based is readily ascertainable. PROC. ZOOL. S O C - 1888, No. XV. 15 |
