_Lingua ovata, posticè libera, rotundata; anticè subacuminata. Dentes
palatini in fasciculis binis plùs minùsve obliquis, pone nares
posteriores positi. Tympanum celatum. Digiti anteriores haud
palmati; posteriores ad basin tantùm cute connexi. Glandulæ cutaneæ
nullæ. Sacculi vocales (maris) utrinque sub lingua nascentes._
The two species on which I have founded this genus approach so nearly to
some species of _Cystignathus_, that it is not without hesitation that I
determine on considering them as typical of a new generic form. The
principal characters on which I have founded the distinction are the
position of the palatine teeth, the form of the tongue, the concealment
of the tympanum, the absence of glands and pores on the skin, and the
connexion of the base of the hinder toes by a rudimentary palmar
membrane. It is true that some of the species of _Cystignathus_, as that
genus is at present constituted, agree with the present form in some or
other of these particulars; but upon the whole they are sufficiently
distinct; and in fact the genus _Cystignathus_, as left by M. Bibron,
appears to me to stand in need of revision and dismemberment. The
species constituting the genus now proposed, are however both new. The
genus _Borborocœtes_ will probably stand, in its natural affinities,
between _Cystignathus_ and _Cycloramphus_, from the latter of which it
differs in the situation of the palatine teeth, in the degree to which
the hinder feet are webbed, and the comparative length of the hinder
legs. The two latter characters are of importance as indicating a
difference of habit; and we find that _Cycloramphus_ has proportionally
short hinder limbs, with the toes extensively palmate, whilst in
_Borborocœtes_ the hinder legs are much longer, and the toes scarcely at
all webbed. The former structure indicates a greater power of swimming,
and the latter of leaping.
_Reptiles. Plate 17._
[Illustration:
_Drawn from Nature on stone by B. Waterhouse Hawkins._
_Printed by C. Hullmandel._
]
_1._ _Borborocœtes_ _Bibronii._ _1a. Mag. View of Tongue & Gullet._
_Nat. Size._
_2._ _Grayii._ „
_3._ _Pleurodema_ _Darwinii._ „
_4._ _elegans._ „
_5._ _bufoninum._ „