1925] Storer: A Synopsis of the Amphibia of California 207 
cumstances. In outline and in coloration these hylas simulate their 
environment, so that, to the human eye, they may pass as small pro- 
tuberances on the rocks, (Compare pi. 2, fig. 4, and pi. 13, figs. 37, 38.) 
Indeed, if a person is seeking to collect these hylas it is often desirable 
to stand and give close scrutiny to the rocks close at hand, whereupon 
one or more hylas will often be discerned where a hasty glance might 
have failed to detect them. As part of this scheme which results in 
the animals escaping observation, they remain absolutely quiet, even 
on the close approach of a person, so that it is often possible to walk 
slowly but directly up to where one of the animals is located and with 
a quick movement capture it in place. 
On March 25 and 26, 1923, I visited the lower reaches of Tahquitz 
Creek, near Palm Springs, Riverside County, for the purpose of study- 
ing the habits of arenicolor. The creek is inhabited by this hyla down 
almost to where the waters disappear into the sands of the Coahuilla 
Desert. During the day the hylas did not come particularly to notice, 
except when hunted for, but with the approach of evening the voices 
of the males were much in evidence. 
Many of the creeks which come down from the mountains of south- 
ern California have their sources during the winter and spring months 
in banks of snow. When the sun leaves the mountain in the afternoon 
the melting of the snow 7 lessens or stops and the creeks carry slightly 
lesser quantities of water. Their courses being short, the water in the 
desert end of the streams soon drops an inch or so. The males of Hyla 
arenicolor then take position for the nightly chorus. Usually they 
sit solitarily on the narrow strip of wet sand left exposed along the 
bank by the lowering of the water ; occasionally one takes shelter in 
a crevice between tv 7 o rocks. In practically all cases there is a rock 
above the animal which acts as a shelter against the approach of 
enemies from the shore side and also probably serves to some extent 
as a sound reflector. The male hylas sit with their backs to the shore, 
facing the stream, toward the center of which they direct their vocal 
effort. (The females of this species are not know r n to leave the creek 
at any time.) Each male sits with hind legs in the usual position 
with 'knee-joints’ out and tarsi touching, v 7 hile the front feet are 
beneath the body but with the legs spread apart so as to leave 
space beneath the front of the body. This brings the chin up so that 
the vocal pouch does not touch surrounding objects when it is ex- 
panded. These animals do not croak so persistently as Hyla regilla. 
One individual will give ten to fifteen notes, then have a quiet spell of 
