he narrower
groups of vomerine teeth, clearly distinguish this western Mexican form
from the more robust, larger _melanonotus_ to the south. The call is
likewise fainter and different in quality." Concerning the glands,
Taylor (_loc. cit._) remarked: "There is a possibility that the horny
excrescence covering the glands may appear only during the breeding
season. This character is quite as strongly marked in females as in
males." Bogert and Oliver (1945:324) concluded that the population of
_Leptodactylus_ in northwestern Mexico could not be distinguished from
_melanonotus_ in other parts of the country and thus synonymized
_Leptodactylus occidentalis_ with _melanonotus_. Bogert and Oliver (op.
cit.: 324) stated that the extent as well as the presence or absence of
ventral glands was highly variable in all samples examined by them.

Upon seeing numerous living individuals of _Leptodactylus melanonotus_
from many parts of its range in Mexico and individuals of the population
of _Leptodactylus_ in northwestern Mexico (Nayarit and Sinaloa), I was
immediately impressed not so much by the differences in the development
of the ventral glands, but by the color of the glands. The differences
in color are apparent in freshly preserved specimens. With the exception
of _Leptodactylus_ from northwestern Mexico, specimens of _melanonotus_
from throughout Mexico and northern Central America have yellow or
yellowish brown glands. Specimens from northwestern Mexico have black or
brownish black glands that are conspicuously darker than those found in
_melanonotus_. Examination of 653 preserved specimens of _Leptodactylus
melanonotus_ from Mexico and Guatemala has failed to reveal specimens
with black ventral glands, like those found in specimens from
northwestern Mexico, to which the name _Leptodactylus occidentalis_ has
been applied. Furthermore, in _melanonotus_ the glands are less distinct
and more extensive than in _occidentalis_; in the latter species glands
are absent from the throat and midventral area, where they often are
present in _melanonotus_ (Fig. 7).

In some individuals of both species collected in the dry season and in
some collected in the rainy (breeding) season the glands are absent; the
development of these glands, therefore, does not seem to be correlated
with breeding. Likewise, the glands are present or absent in either sex,
and often as not they are present in juveniles. Presence of the glands,
therefore, canno