head like a watchspring. The shell is about an inch long, while the 

 radula, when stretched out, measures two and a half inches. This great 

 length is necessary because it rapidly wears out on the front end while 

 scraping the algce from the rocks, and the worn part must be quickly 

 replaced. The shells of the northern species are not very handsome, 

 being black, brownish, or yellow, but some of those living in the tropics, 

 as the lAttorina angullfera, are very attractive, their shells being taste- 



A good locality for Littorinas, Newport, Rhode Island. 



fully mottled. All of the species are amphibious, living for a long time 

 out of the water. It is recorded that several specimens of a \Yest 

 Indian species lived in a gentleman's cabinet for over a year. 



A genus of small shells related to lAttorina is Lacuna, the animal 

 of which presents a good example of protective coloration. It feeds upon 

 seaweed, and when the weed is brown the animal becomes brownish; 

 when the weed is red the animal is of a rosy tint. 



A singular genus of mollusks is the Vermetus, or worm shell, which 

 is frequently mistaken for a true worm. The shell of a Florida species 

 is ten inches long. It starts out like other shells, but after making six 

 or eight whorls it suddenly forms a long, irregular tube. In an allied 

 genus, Turritella, or the screw shells, the whorls are from twenty 



100 



