AIR-BREATHING SNAILS AND SLUGS 267 



touched it secretes a glutinous mucus. It is liable to 

 become a great pest in gardens, doing most of its rav- 

 ages in the night season. 



Limax campestris^ Binney, the Lawn Limax, is 

 closely related to the last species, but it is smaller, 

 more semi-transparent, and does not so readily se- 

 crete mucus. It i^ about an inch long, the body is 

 cylindrical, the mantle oval and fleshy, the back 

 tubercled and furrowed, the foot narrow and whitish. 

 It has no spots or markings, and it varies in color 

 from amber to black. I have sometimes seen great 

 numbers of these little black slugs upon the lawn at 

 Mills College, especially in the spring time. 



Limax hezvstoni^ J. G. Cooper, Hewston's Limax, 

 is found in San Francisco, Los Angeles, and other 

 places. It is a dark colored slug, two inches long, the 

 back being strongly ridged and higher than the front 

 of the body. The height of the body is twice the 

 width of the foot, the base of which is whitish in 

 color. 



Vitrina pfeifferi^ Newc, Pfeiffer's Glass-snail, is a 

 little mollusk resembling a slug, but with a small, 

 shining, greenish-white shell of three whorls, 5 mm. 

 in diameter. The aperture is large, the lip thin, and 

 the shell too small to admit the whole animal. It is 

 generally found at high altitudes, in California and 

 eastward. 



Several species of the genus Zonites and its allies 

 now follow in our train of study. They are all 

 small, having spiral shells, usually with rounded 

 whorls and an open umbilicus. 



Vitrea cellaria. Mull., {Zonites cellarius), the Cel- 



