230 Variation in Shells. [ ZOE 
extremely scarce, so scarce that the researches of the collector would 
not be rewarded by twenty-five specimens in a whole day’s search. 
“Facts are stubborn things.” I now offer measurements with 
notes on sculpture and color variations of some of our West Coast 
land shells restricted to limited areas, and collected by myself, 
which will, I think, confirm my opinion that species restricted to 
limited areas often exhibit great variation. 
felix intercisa Binney.—San Clemente Island, California. This 
species, by its sculpturing and form, stands at the head of a small 
group of shells restricted in their range to the islands off the coast 
of California. In its wanderings among this group of islands it has 
become somewhat modified in its sculpturing, form and color, and 
on these modifications conchologists have made two other species 
which we know as Helix Ayresiana Newc., and Helix 7) ryonit Newc. 
I may also add here that this group of shells is very closely con- 
nected through varieties of H. Ayresiana with the form we know 
as f7. Traskii, and was perhaps evolved from the group of 17. fidelis 
through H. Traskit. 
Measurements of Helix intercisa, restricted to the Island of San 
Clemente. Largest specimen: greatest diameter, 27 mm.,; altitude, 
18 mm. 
Var. minor. Smallest specimen: greatest diameter, 18 mm.; al- 
titude, 11 mm. Uniform light-yellowish chestnut color, with and 
without a band, and varies very much in form and elevation or 
depression of spire. 
Var. elegans. Uniform ashy-buff color, faintly banded and vari- 
able in form. 
‘Var. nepos. Uniform ashen-white; spire horn color, variable in 
_ form and sculpturing. 
Var. albida. Uniform milk-white, sometimes with a faint band 
at the periphery; sculpture nearly obsolete. 
Helix Ayresiana Newc., San Miguel Island. 
In sculpturing this shell stands next to HY. intercisa in the group. 
The revolving lines are less crowded and more regular in their 
arrangement, while the transverse striz or lines of growth are some- 
_ what rib-like on the body whorl. The umbilicus js open or half- 
covered, while in Helix intercisa it is sealed up. 
Largest specimen: greatest diameter, 28 mm. ; altitude, 13 mm. 
Smallest specimen: greatest diameter, 17 mm.; altitude, 13 mm. 
