_Cristâ suprà humeros humiliore; digitis ferè equalibus subpalmatis;
caudâ compressâ._
_Amblyrynchus Cristatus._ Bell, Zool. Journ. 1825, p. 195. Tab. Supp.
XII. Bibr. Hist. Rept. 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 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 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 _Amblyrynchus cristatus_ inhabits
the coasts of all the islands, the other species is found only in the
central portion of the group.
GENUS—LEIOCEPHALUS. _Gray._
LEIOCEPHALUS GRAYII.