AIR-BREATHERS 121 
well fed. While speaking of food we may remark 
that they are remarkably fond of orange peel, and 
will be pretty sure to find a piece if it is left near 
their haunts, a fact indicating that they have a 
keen sense of smell. They are also fond of milk. 
The name of this species is Ariolimaa columbi- 
anus, Gld., the ‘‘Great Yellow Slug.’’ Occasion- 
ally a specimen is found that is parily covered 
with large, dark spots, but at best it is only a spot- 
ted form of the main species. A variety stramin- 
eus, Hemphill, of a light straw color, is described 
from Santa Cruz Island. 
Two other species, Ariolimax californicus, J. G. 
Cooper, and Aphallarion buttoni, Pils. & Van., can- 
not be readily distinguished from A. columbianus 
by external characteristics, though they differ in- 
ternally, particularly in the genetalia. Proper ref- 
erences for their extended study are made in the 
-List. 
Ariolimax niger, Cooper, the Black Slug, has a 
body long and narrow, blunt in front and tapering 
but little behind. When crawling, the animal is 
some two inches in length, but when at rest, as it 
may be found under old boards and in similar 
places, it is so contracted that it is hardly one inch 
long. Its color is quite dark, sometimes being 
nearly black, especially on the upper surface of 
the body; but I have found specimens which are 
very much lighter, almost an ashy gray. This 
species 1s common in central California. 
Ariolimax hemphili, W. G. Bin., Hemphill’s 
Slug, is a small, slender, flesh-colored slug, with a 
