THE NAUTILUS. 93 



which can be cast off and renewed whenever occasion requires. 

 There are a large number of genera and species ; they are distrib- 

 uted world-wide, in all seas and at all depths from low water to 240 

 fathoms. Fossil arks are abundant in all ages. There are several 

 groups of this family, one of which is sedentary in its habits, adher- 

 ing to crevices in rocks ; another group Scaphula Benson, an East 

 Indian genus, lives in fresh water, a thousand miles from the ocean ; 

 others live in sand or mud and move about freely. We have two 

 6pecies in New England, although a third, Area ponderosa Say, is 

 occasionally washed up on the beach at Edgartown, Martha's Vine- 

 yard. 



200. Area (Argina) pexata Say, 1822. 



Shell oblong, thick and solid, very inequipartite ; beaks prominent, 

 ventricose, pointing obliquely forwards, terminating in points which 

 are nearly in contact, surface with 32 to 36 broad radiating ribs, 

 crossed by minute lines of growth, the whole covered with a very 

 coarse, brown hairy epidermis ; interior white, the margin polished 

 and deeply crenulated by the alternate termination of the ribs and 

 grooves ; hinge with a series of small teeth. Length 2^ inches, height 

 2 inches, breadth 1^. 



This species is very abundant in Narragansett Bay and has been 

 quoted from Cape Cod to Gulf of Mexico. 1 think it must be very 

 rare and local south of Long Island Sound, as collectors south of 

 New York seem to consider it a rare species. It is distinguished 

 from all others of our marine shells by its rough, dirty epidermis, 

 which is thick and hairy, generally detached in places and can be 

 torn off in long strings. The fishermen call it the hairy clam. It is 

 not an attractive looking object when found alive, and is still more 

 repulsive if we open the valves, for the animal then exudes a reddish, 

 bloody-looking liquid, from which circumstance it is often called the 

 bloody clam. 



201. Area (Scapharca) transversa Say, 1822. 



Shell transversely oblong, rhomboidal ; beaks prominent, separated 

 from each other by a long, narrow space ; surface with 32 or more 

 radiating ribs, the ribs and intervening spaces of about equal breadth. 

 Length and breadth about 1^ inches each, height 1 inch. This spe- 

 cies is of southern distribution and is not at all common as far north 

 as Rhode Island. It has been found from Florida to Cape Cod. 



