1918.] NATURAL SCIENCES OF PHILADELPHIA. 285 
and robust Sonorella was found at a low elevation in a barrier of 
boulders, so dry and barren the snails would necessarily lie dormant 
a large part of the year. At a thousand feet higher, beside a stream 
of running water, came in a much smaller breed; and, 1500 feet 
above number two, with an ideal situation as to a moist atmosphere, 
food, shelter and snail comfort, lived a pigmy Sonorella of about 12 
millimeters in diameter. 
Again on the Kaibab Plateau in 1909, every colony of Oreohelix 
strigosa depressa seemed a little different from all other colonies. 
At Two Spring Canyon with running water all the way, the pigmies 
were at the higher station in a grove of quaking asp. Every colony 
increased in size and color brilliance at a regular pace down the 
canyon. Here seemed proof positive of the advantage of a longer 
growing season. Over the ridge in Snake Gulch the order was re- 
versed, for the larger shells were at the top in a dry situation, and 
their size seemingly decreased in proportion to the mileage as we 
descended along a running stream. In Jacobs Canyon, running 
parallel to Snake Gulch, dry all the way, the large and gaudy shells 
were midway, the smaller and paler above and below. Food condi- 
tions may have had some influence in the development of these 
races but if so the evidence was not apparent. In the field we meet 
contradictions continually beyond our understanding, but perhaps 
we may have a better comprehension before the survey of the South- 
west is completed. 
HELICID A. 
Sonorella odorata n.sp. PI. III, figs. 1 to 4. 
The shell is depressed, umbilicate, the umbilicus contained about 
7% times in the diameter of shell; buffy-citrine below, somewhat 
lighter than isabella color above, with a chestnut brown band at the 
shoulder. The first half whorl has irregular radial wrinkles soon 
passing into a low granulation, the last embryonic whorl granular, 
over which there are close decurrent threads, interrupted into short | 
dashes on the upper part of the whorl. Subsequent whorls are 
very minutely granular, somewhat dull, the granulation effaced at 
the base, which is more glossy. The last whorl shows also numerous 
faint spiral striae. The whorls are quite convex, the early ones 
increasing slowly, the last widening rapidly, rather abruptly descend- 
ing close to the aperture. The aperture is elliptical-lunate; peristome 
is narrowly expanded throughout, dilated at the columellar insertion. 
Alt. 11.4, diam. 19.5 mm.; 44 whorls (type). 
ameter toi. <6 Cae 1 (Station 18: 1917): 
Spioees hres 2a «(tation 18, 1917). ; 
