MARINE MOLLUSCA OF THE UNITED STATES. 15 



Length of spiral portion from one-half to one inch ; the irregu- 

 lar prolongation or tube sometimes eight or ten inches. Animal 

 light brown, spotted with black ; mantle margin fringed ; bran- 

 chial plume large and long, nearly in the middle of the back ; 

 foot very short and broad, dilated into rounded auricles ante- 

 riorly; the muzzle is broad, not cleft; tongue small; tentacles 

 short, conical; the eyes at their external bases. An elevated 

 ridge runs along the back, becomes flattened into a membrane at 

 the head, and passes round under the right tentacle, forming a 

 kind of canal, near which is the anus. Operculum corneous, con- 

 centric, black, and hard on the inner, and lamellated on the outer 

 surface. 



Eggs deposited in July ; soft, slightly cohering in the form of 

 an elongated cone, bent into a half circle. 



Massachusetts ; North Carolina. 



Genus CJECUM, Fleming. 

 Edinb. Encyc., vii. 1824. 



Shell minute when young, discoidal when adult, decollated, 

 tubular, cylindrical, arcuated; aperture round, entire; apex closed 

 by a mammillated septum, marking the point at which the origi- 

 nal spire has been cast off. 



The animal has a long and flat rostrum ; tentacles short, sub- 

 clavate at the tips ; eyes sessile behind the bases of the tentacles; 

 mantle thick, fleshy, circular, closely embracing the neck; a single 

 branchial plume ; foot short, narrow, truncate in front, obtuse 

 behind. 



1. C. PULCHELLUM, Stimpson. Fig. 135. 



Proc. Bost. Soc. Nat. Hist., iv. 112. 1851. 



Shell clavate, arcuated, contracted at both extremities, and 

 angular on its dorsal line; thick, pale yellowish-brown, with about 

 twenty-five strong, rounded ribs. 



Length 2.5, diam. .375 mill. 



The head projects but little in advance of the foot, which is 

 short ; the muzzle is cleft and transversely wrinkled, with two 

 black spots above, just in front of the tentaculae, which are thick, 

 curved, and covered with large vibrilhe ; eyes conspicuous, black, 

 oval, near the middle of the bases of the tentaculge. 



Low water to 15 fathoms. 



New Bedford Harbor. 



