| ...
| | | | |
_H. crassa_ | 1 | 53.7 | 0.50 | 0.33 | 0.28
---------------+----+-----------+-----------+-----------+-----------

Frogs in this group are rather drab in appearance. The dorsal color
varies from dull green to various shades of brown. The most distinct
aspect of the coloration is the different color patterns on the flanks
and posterior surfaces of the thighs. The flanks in all species are
marked with spots or reticulations.

_Hyla bistincta_ differs from other members of the group in having
vocal slits and a distensible vocal sac. Only this species has been
reported to call (Shannon, 1951:473). Insofar as is known, the other
species are mute. Examination of skeletal preparations of _H.
bistincta_, _charadricola_, and _robertsorum_ and X-rays of the other
species shows no notable specific differences in the osteology. Since
the tadpoles of only _H. bistincta_ (Duellman, 1961:47) and _H.
robertsorum_ (Rabb and Mosimann, 1955) are known, larval characters
are of limited use in intra-group systematics.

Key to the Species of the _Hyla bistincta_ Group

1. Snout, in dorsal profile, short and bluntly rounded;
canthus rounded, sometimes indistinct, vocal slits absent 2

Snout, in dorsal profile, longer, squared; canthus distinct,
vocal slits present or absent 4

2. Feet webbed to base of discs; dorsum dull olive green;
flanks having cream-colored spots _H. crassa_, p. 486

Feet not webbed to base of discs; dorsum brown 3

3. Tarsal fold strong; thoracic fold heavy; webbing on feet
extending to middle of penultimate phalanx of fourth toe;
distinct white stripe above anus; cluster of largo spines on
thumb in breeding males, _H. pachyderma_, p. 485

Tarsal fold weak and short; thoracic fold absent or barely
indicated; webbing of feet extending to base of penultimate
phalanx of fourth toe; no distinct white stripe above anus;
nuptial tuberosities in breeding males consisting of small
spines _H. robertsorum_, p. 481

4. Tarsal fold strong; anal flap elongate; anus opening at
lower edge of femur; dorsum tan or brown; flanks mottled with
cream and brown; venter immaculate creamy white; no anal
stripe; vocal slits present, _