REPTILES. 23. 



Amblyrynchus cristatus. Bell. 

 Crista supra humeros humiliore ; digitis ferh equalibus subpalmatis ; caudd compressa. 



Ambli/rynchus Cristatus. Bell, Zool. Journ. 1825, p. 195, Tab. Supp. XII. Bibr. Hist. Kept. IV". p. 204. 



I established the genus Amblyrynchus nearly eighteen years ago, from a 

 stuffed specimen of the present species, which had 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 descrip- 

 tion which arose from drying and bad stuffing. Mons. Bibron also took his de- 

 scription 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 com- 

 pressed throughout its whole length ; and with regard to the toes no mention is 

 made of their being partially xmited 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 might 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 Amblyry7ichus cristatus inhabits the coasts 

 of all the islands, the other species is found only in the central portion of the 

 group. 



