26 



ORDER TRACHELIPODA. 



The Trachelipodes contain by far the largest portion of 

 the univalve shells, and are mostly inhabitants of the 

 waters. They form two numerous groups, the feeders 

 on animal food, (Zoophagi,) and those that exist on 

 vegetable substances, (Phytophagi.) The animal feeders 

 are well distinguished from the other group, by having 

 a mouth w^ithout jaws, being furnished with a tube 

 which they can retract or advance at pleasure, for the 

 purpose of sucking their nutriment from the bodies of 

 other inhabitants of the deep. The animal feeders are 

 also known from the other section by the possession of 

 a projecting tube called a siphon^ which conveys the 

 water to the gills. The shell also points out to which 

 section its possessor belonged, from the lower part of its 

 opening being formed either into a sort of canal, or a 

 groove for the reception of its siphon. They are all 

 marine animals, and breathe water. The tiesh-eating 

 tribes compose five families. 



Family Convoluta, (rolled vp like a scroll.) 



Family Columellaria, (disthiguished hy a ■plaited columella.) 



Family Purpukifera, (yielding a purple colour.) 



Family Alata, (witiged.) 



Family Canai.ifera (having a canal at the base of the opoiing.) 



Family CONVOLUTA. 

 The convoluted shells contain but few genera; but these 

 are very rich in species, and furnish us with some of the 

 most beautiful specimens of this class. 



