e tadpoles of this species were described by Rabb and
Mosimann (1955). Tadpoles obtained from streams at 3.3 kilometers
north and at 8.5 kilometers southeast of Zacualtipan, Hidalgo, are
like those described by Rabb and Mosimann in having 2/3 tooth rows,
peglike serrations on the beaks, and long rounded tails. The largest
tadpole (KU 60078) has small hind legs, a body length of 22 mm., and a
total length of 61 mm.

_Remarks._--Taylor (1940:393) found frogs of this species in plants
along small spring-fed rivulets in an open meadow at El Chico
Parque Nacional. Also, he noted that active frogs dove into the
streams and took refuge in the mud on the bottom. Rabb and
Mosimann (1955:1) found this species along banks of tiny streams
in open meadows and noted that the frogs sought refuge in the
water. At El Chico Parque Nacional on June 8, 1960, I found _Hyla
robertsorum_ under rocks along small rivulets by day; at night, when
the temperature was 14 deg. C., frogs were sitting on rocks and in
junipers overhanging a small stream. At the same locality on June
23 and 24, 1962, frogs of this species were found on rainy nights,
when the temperature varied from 10 to 12 deg. C. At this time the
frogs were sitting on the grassy banks of rivulets in the meadow.
During the day _Hyla robertsorum_ was found on the earthen banks
of the rivulets in places where dense growths of grass overhung
the streams. On December 23, 1959, one specimen of _Hyla robertsorum_
was found beneath a rock in a small stream in pine forest at
3.3 kilometers north of Zacualtipan.

Rabb and Mosimann (1955:1) obtained tadpoles of _Hyla robertsorum_
from quiet pools of a stream at El Chico Parque Nacional. I
found tadpoles in pools in rocky streams in pine forest at 3.3 kilometers
north and at 8.5 kilometers southeast of Zacualtipan. Four
completely metamorphosed juveniles obtained on June 8, 1960, at
El Chico Parque Nacional have snout-vent lengths of 30.6 to
32.0 mm. Gravid females were found at the same locality on June
8, 1960, and June 23, 1962.

[Illustration: FIG. 4. Map showing locality records for
_Hyla crassa_, _Hyla pachyderma_, and _Hyla robertsorum_.]

_Distribution.--Hyla robertsorum_ inhabits streams in the pine and fir
forests in the higher parts (2250 to 3050 meters) of the Sierra Madre
Oriental in extreme northern Puebla and eastern Hidalgo (Fig. 4).

Specimens examined.--HIDALGO: 16 km. W Agua Blanca, UMMZ 106432 (6);
El Chico Parq