transferred to _Syrrhophus_ by Dixon (1957), who redefined
_Tomodactylus_ and added more species to the genus.

Since beginning my studies of the Mexican leptodactylids in 1962, I
have become acutely aware of difficulties involved in defining the
genera. A revision of _Eleutherodactylus_ and a review of _Syrrhophus_
are nearing completion, but prior to their publication it is desirable
to redefine the genera of the Mexican leptodactylids, and in so doing
recognize an heretofore unnamed genus. The definitions of
_Eleutherodactylus_ and _Leptodactylus_ may need to be altered in the
future, since both are widespread in South America and occur in the
West Indies. Their definitions as given here are as precise as present
knowledge permits. _Syrrhophus_ and _Tomodactylus_ are small
assemblages that occur only in southwestern United States, Mexico, and
Guatemala.

Taylor (1952) synonymized _Engystomops_ with _Eupemphix_ which,
although related, should be regarded as generically distinct (Gallardo,
1965). Perhaps the most conservative classification is that of Myers
(1962) who, without published evidence, combined _Eleutherodactylus_,
_Syrrhophus_, and the South American _Lithodytes_ in a single genus.

The major problem for students working with the Mexican leptodactylids
has not been the separation of _Engystomops_ or _Leptodactylus_ from
other genera but the separation and definition of the eleutherodactyline
frogs currently placed in three genera, _Eleutherodactylus_,
_Syrrhophus_, and _Tomodactylus_. As will be shown in this paper, these
are more conveniently placed in four genera. Once a fourth genus is
recognized, certain phylogenetic problems disappear and a reasonable
zoogeographic interpretation is possible for Middle American
leptodactylid distribution.

ANALYSIS OF CHARACTERS

In Mexico and northern Central America approximately 55 species of
eleutherodactyline frogs (_Eleutherodactylus_, _Syrrhophus_, and
_Tomodactylus_) are known. Four genera can be recognized on the basis
of the nature of inguinal glands, morphology of the hands and feet, and
certain osteological features.

[Illustration: FIG. 1. _Tomodactylus angustidigitorum_ (UMMZ 114305,
x 4.5) illustrating the lumbo-inguinal gland typical of members of the
genus. From a kodachrome by Wm. E. Duellman.]

Glands

Leptodactylids have a variety of glands that have been used as generic
characters. Smith and Taylor (1948) regarded the so-called