1 66 WILSON. [VOL. I. 



Habits. - - This species lives in the mud near and below ordi- 

 nary low-water mark. It can be best obtained during the few 

 days of each month when the tides run lowest, at which time 

 it can be dug in the same way as the common clam (mya). 



It is most abundant in close proximity to mussel beds where 

 the mud is soft and very black with organic matter. 



I am aware that this habitat is radically different from that 

 given by Greef and others for E. Pallasii, but I find a ready 

 explanation in the fact that sand beaches are the rare exception 

 rather than the rule along the Maine coast, so that the animal 

 has simply accommodated itself to its environment. 



Its home is a simple burrow formed by pushing aside the 

 mud. The manner in which this is done was repeatedly ob- 

 served both in its native haunts and in an aquarium. 



If not already in that position, the animal turns until it rests 

 upon its ventral surface. This brings the two large anterior 

 setae in contact with the mud. The proboscis is now turned 

 upward and backward, until it lies along the dorsal surface of 

 the body, with its own ventral surface outermost, but protected 

 somewhat by a rolling in of its edges. The proboscis remains 

 inert in this position and takes no part ivhatever in the burrow- 

 ing. This is in strong contrast to the active locomotor use of 

 the proboscis described by Rietsch in a specimen of Boncllia 

 minor (i i). By a series of muscular contractions, which include 

 both the longitudinal and circular muscles of the body walls 

 and the special muscles which move the ventral setae, these 

 latter are thrust forward until they project in front of the body 

 almost horizontally. 



At the same time the base of the proboscis is drawn back- 

 ward and somewhat upward, so that the anterior end of the 

 body becomes wedge or chisel shaped, the ventral surface being 

 flattened and extending farthest forward, with the two setae pro- 

 jecting from its anterior edge. These setae are then turned 

 downward and thrust into the mud as far as possible. Being 

 curved, they furnish an excellent leverage, and the body is 

 drawn toward them by a contraction of the longitudinal muscles. 



This contraction passes slowly backward along the body 

 until the posterior end is reached, which is moved forward 



