1922] NATURAL SCIENCES OF PHILADELPHIA 91 



Canyon (on both slopes), and more especially at the mouth of 

 Tahquitz Canyon. He must have happened on a remarkably 

 favored location at a fortunate time, for on the later expedition 

 we failed to meet with living specimens in any numbers anywhere, 

 whereas only a week before he had taken over a hundred in the 

 open at the latter locality alone. On that occasion he found the 

 snails abundant and crawling actively on the surface among big 

 slabs of granite and under bushes on quite a moist slope, where 

 they seemed to constitute quite a definite colony. The time was 

 between 8:00 and 9:30 A. M. In Murray Canyon where he had 

 collected the previous afternoon, Mr. Smith found dead shells 

 fairly common on both slopes of the canyon along its lower course, 

 but live shells were only scattering and mostly to be found under 

 stones, indeed only one being found crawling on the surface. In 

 this canyon he could detect no indication of any association in 

 colonies, and we found conditions in Palm. Canyon altogether 

 similar in this respect. The slope back of the Palm Springs Hotel, 

 which, by the way, impressed us as by no means the best collecting 

 ground, is reputed to be the type locality. This was our Station 

 IV, or at any rate not far from it. 



Orcutt ('90, p. 67) has already recorded a snail which he collected 

 at Snow Creek Canyon as Helix traskii, but at that time the 

 peculiarities of the desert snails were little understood, and I think 

 there is small doubt that his shells were really wolcottiana. The 

 fact that we collected indubitable specimens of the species so 

 near there and actually to the west supports this contention. 

 True Epiphragmophora traskii is still unknown from the desert 

 drainage. 



As is brought out in the table of measurements, wolcottiana is 

 an extremely variable species even within the confines of a single 

 circumscribed colony like that found at the mouth of Tahquitz 

 Canyon. Some are fairly depressed, some strongly elevated, some 

 large, some with less than one-half the bulk, some extremely thin, 

 some thick and heavy, some with the narrow umbilicus left nearly 

 free, others with it entirely closed, and so on. The color of the 

 animal, too, shows a considerable range of variability, though 

 always strikingly different from, that, for instance, of the following 

 species. On the other hand the shells of adults vary little in color. 

 Young shells are always much darker and brighter than adults, 

 their bright snuff brown color being quite unlike that of any other 

 species of desert snail. 



