CHAPTER LX: THE SHELL-BEARING SEA 



SLUGS 



Sub-Order Tectibranchiata 



This division embraces families of the Order Opisthobran- 

 chiata, in which the shell is seen to disappear by gradual changes, 

 becoming thinner and more enveloped in folds of the mantle 

 and foot as it diminishes in size. The right gill is usually present, 

 but concealed by the mantle fold. The group is not well repre- 

 sented in American waters. 



THE CANOE SHELLS 



Family ScApHANDRiDyC 



Genus SCAPHANDER, Montf. 



Shell scoop-like, gaping, scarcely containing the body. The 

 tentacles are united forming a broad lobe behind the large head. 

 The gizzard is large and very powerful, enabling these creatures 

 to devour good-sized mollusks and reduce their thick shells. 

 They subsist chiefly upon tooth shells, in search of which they 

 burrow persistently in the sand. 



The Woody Canoe Shell (S.lignarhis, Linn.), with brownish 

 orange surface grained like fir wood, and white lining, is the type 

 and by far the largest of the canoe shells. Length, 2 to 2| 

 inches. 



Habitat. — Coasts of Great Britain, Norway and Mediter- 

 ranean Sea. 



S, lineolatus, Couth., closely striated, yellowish, with 

 spreading outer lip, one-half inch long, is found in Massachusetts 

 Bay. A white one, a trifle longer, occurs in Casco Bay. 



243 



