OCR Text |
Show vi PREFACE. well-known and very common circumstance with regard to several groups of animals. In our present researches there exists a remarkable example of this fact in the genus Pt·octot1·etus, consisting, as is now known, of at least fourteen species, all inhabiting the western coast of South America. These facts, interesting as they are, have never been sufficiently investigated, although, it must be confessed, there are so many anomalies in relation to this subject, that we must despair of ever reducing the facts in question to any thing like fixed laws. The close approximation of the Raniform and Hyliform groups of the Anourous Amphibia is strikingly illustrated by several new forms obtained by Mr. Darwin, which are so perfectly osculant between the two families, that it is difficult to assign them a decided location. And the addition of some bufonine forms in the family Ranidm, as at present constituted, and on the other hand of some amongst the Bufonidce, which are no less raniform in their general structure and habits, render it increasingly probable that the single character of the presence or absence of superior maxillary teeth, must be considered as insufficient to constitute alone a natural distinctive family character. There arc several minor points bearing upon the natural arrangement of the Anourous Amphibians, which are illustrated by the characters of some of the species now first described, which will doubtless at some future time assist in the construction of a classification of these animals, bearing at least a nearer approximation to their natural arrangement than any that has hitherto been promulgated. The Ophidians have been placed in the hands of Mons. Bibron, who is at the present time engaged in completing his admirable history of Reptiles, by the publication of those volumes which are devoted to this order; and it must be considered a fortunate circumstance that the delay which has taken place in the appearance of tl.tat portion of his labours, bas thus afforded the opportunity of embodying in so perfect a work, the numerous discoveries of Mr. Darwin in this particular department of Erpetology. T. B. Hornsey, Sept. 2, 1843. REPTILES. TniBus-EUNOTES. Bibron. F AMII.IA- TROPIDURIDJE. Milti. TROPIDOLEPIDIENS. Bibr. GENus-Tropidurus. (Iu part.) Weigmann. PnocTOTRETus. Bibr. CnARACTER GENERrcus.-Pori f emorales nulli. P ori prw-anales in maribus tan tum. Urista dcrsalis nulla. Dentes p alatini. Squama; imbricatro ; dorsales carinatre. TaE ~enus which I take the present favourable opportunity to illustrate, formed a section or sub-genus of the genus Tropidur~es, according to Weigmann, who, however, was acquainted with two species only; Pr. Cltilensis and Pr. nigromaculatus. Of the varieties of the former of these, that author has made no less than three species; but these have been very properly reduced by M. Bibron to one only. Th~ last-named excellent erpeto1ogist described several additional species, whiCh had been bronght from Chile, by M. D'Orbigny, and others; and I received, some years since, from Capt. King, three or four species which were found by him. in the same locality, in the course of his well-known survey. Tl1e number of species altogether, hitherto known, amounts to ten; to which I have nnw the opportu~~ty of adding four entirely new, forming part of the interesting collection of Rep.tiha made by Mr. Darwin. One of them, Pr. Kingii, was already in my collectwn, amongst those which were given me by Capt. King. The genus, therefore, of which, but lately, two species only were known, now consists of fourteen ; and it is highly probable that more may yet be obtained by more prolonged and extensive investigation in the same districts. B |