AIR-BREATHERS 117 
Selenites duranti, Newe., Durrant’s Selen, is a 
little affair, 4mm. across, widely umbilicated, flat- 
tened, light yellowish brown, striated. Var. cae- 
lata, Mazyck, is about the same size, but has very 
coarse, rough, irregular ribs, seen best from the 
under side. California coast and islands. 
It may be well to remark that all the Selens are 
said to have very vigorous appetites, and they 
should not be placed with other snails, for if they 
are thus confined, the other snails are apt to dis- 
appear. 
The members of the genus Limax are true slugs, 
i. e., they are naked, crawling mollusks, looking 
like snails without shells. It is true that they 
have rudimentary shells concealed by their man- 
tles, but these are not easily observed. Several of 
our species have come over from Hurope, and are 
settling down in America more to their satisfac- 
tion than to ours. Among the various species we 
mention first, Limax maximus, Linn., the Great 
Limax. This creature grows to a length of four 
inches. In color it is ight brown or ashen, with 
rows of round spots alternating with black stripes. 
It has been reported from San Franciseo, Los 
Angeles, and other coast cities. 
Limax agréstis, Linn., the Field Limax, is an- 
other unwelcome immigrant, now thoroughly nat- 
uralized. Its color varies from whitish to black, 
through various shades of yellow and amber. It 
is usually about an inch long, but when fully 
erown is nearly twice that length. The upper side 
of the animal is marked with longitudinal, shal- 
low furrows, darker than the general surface, 
