t once struck by its similarity to Noble's figures of
transitional types between arciferal and firmisternal forms. The
_Cauphias_ sternum recalls some of his figures for _Sminthillus_ and
_Eleutherodactylus_. This genus is probably most closely related to
the latter and has probably become highly modified to meet some
peculiar environmental condition or on account of some specialized
habits as yet unknown." Kellogg (1932:118) placed _Cauphias_ in the
Leptodactylidae and stated that the terminal phalanges are T-shaped.
Hartweg (1941:1) considered _Plectrohyla_ to be the correct generic
name for _Cauphias guatemalensis_; he thereby relegated _Cauphias_ to
the synonomy of _Plectrohyla_. Hartweg (1941:9) further showed that
the terminal phalanges of _Plectrohyla guatemalensis_ were not
T-shaped and that intercalary cartilages were present. Thus, he
correctly concluded that _Plectrohyla guatemalensis_ (and _P. crassa_
by implication) was a member of the family Hylidae. Stuart (1942:6)
followed Hartweg's allocations and further suggested that _Plectrohyla
crassa_ might be the same species as _Hyla robustofemora_ Taylor. In
his description of _H. robustofemora_ Taylor (1940:392), who had not
examined the type of _Cauphias crassus_, stated that were it not for
the statements of Brocchi and Kellogg that _C. crassus_ has T-shaped
terminal phalanges, "I might suspect I had before me a specimen of
_Cauphias_ closely related to _crassum_."

I have compared the type of _Cauphias crassus_ with that of _Hyla
robustofemora_. With the exception of the minor differences mentioned
in the preceding section on variation, the specimens are alike,
leaving little doubt that they represent the same species. The
statements of Brocchi and Kellogg to the contrary, the type of
_Cauphias crassus_ possesses intercalary cartilages between the
penultimate and terminal phalanges; the latter are not T-shaped, but
as in the type of _Hyla robustofemora_, resemble those typical of
_Hyla_. On the basis of the morphological characters, as pointed out
for _Hyla robustofemora_ by Taylor (1940:392), _Hyla crassa_ is a
member of the _Hyla bistincta_ group.

_Distribution._--This species is definitely known only from a small
stream at an elevation of 2300 meters in the mountains of central
Oaxaca (Fig. 4).

Specimens examined.--OAXACA: Cerro San Felipe, UIMNH 25050. "Mexico,"
MNHN 6331.

RELATIONSHIPS

The evolutionary trend in the members of the _Hy