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Show REPTILES. 23 AMBLYRYNCHUS CRISTATUS. Bell. Crista supra ltumeros ltumiliore ; digitis fe1·e equalibus subpalmatis; cauda compressd. Ambl!Jryncltua OristatU$. Bell, Zoo!. Journ. 1825, p. 195, Tab. Supp. XII. Bibr. I-Iist. Rept. IV. p. 204. I established the genus Amblyrynclt?tS nearly eighteen years ago, from a stuffed specimen of the present species, which bad been obtained by Mr. Bullock, Jun., in Mexico. I had never seen another specimen, until Mr. Darwin brought home a young one from the Galapagos, in excellent preservation in spirits, and thus established its true habitat, and enabled me to correct those errors in my description which arose from drying and bad stuffing. Mons. Bibron also took his description from my specimen, and thus necessarily fell into the same mistakes, of which the most important are those which relate to the form of the tail, and the structure of the feet. Thus the tail is described as " round, excepting towards the extremity, where it is flattened at the sides," whereas it is in fact much compressed throughout its whole length; and with regard to the toes no mention is made of their being partially united by a web or fold of skin, which is the case both on the anterior and posterior feet. These two characters so obviously point out a power of swimming, that the aquatic habits of the species migl1t at once have been predicated, and it is exceedingly interesting to find, from Mr. Darwin's observations, that such is really the case. We have, therefore, two distinct forms -distinct equally in their structure and in their habits-in the two species now described; the one, A. Demarlii, being truly terrestrial, with lengthened, unequal, and distinctly separated toes and a round tail, and the present species as truly amphibious, having short, nearly equal and webbed toes, and a compressed tail. A very interesting account of their habits, &c., is given by Mr. Darwin in his delightful Journal of the Voyage of the Beagle, p. 466 to 472, to which the reader is referred, and which exactly accords with the peculiarities of their respective structure just alluded to. It is remarkable also, that whereas Ambly1'!J'IWltus cristatus inhabits the coasts of all the islands, the other species is found only in the central portion of the group. |