MARINE MOLLUSCA OF THE UNITED STATES. 75 
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 CHCUM, Fleming. 
Edinb. Encye., 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 tentacule, which are thick, 
curved, and covered with large vibrillee; eves conspicuous, black, 
oval, near the middle of the bases of the tentacule. 
Low water to 15 fathoms. 
New Bedford Harbor. 
