LUCINA. 87 
mantle is slightly dentated, and open from the anterior ad- 
ductor throughout the ventral range to near the posterior 
muscle ; it is then closed by a knotty stop, and a linear fissure 
is visible,—I presume, for the dejections,—and then the mantle 
is finally closed. Nothing is ever protruded beyond the shell 
except the foot. The water must reach the branchiz from 
the ventral range. There is certamly on each side the 
mouth, a short, coarse, thick, subcylindrical, striated palpum, 
and I am not sure that there are not a pair on each side. 
The only action of the animal was the exsertion and retrac- 
tion of the foot, which is well represented in the ‘ British 
Mollusca,’ pl. M. f. 6. 
This species is the type of the genus. 
L. rtexvosa, Montagu. 
L. flexuosa, Brit. Moll. i. p. 54, pl. 35. f. 4. 
Exmouth, 2nd June, 1852. 
Animal inhabiting a white, irregularly globular shell, with 
a longitudinal posterior furrow. It was apathetic, and pro- 
truded no organs. On beimg opened, the plain-edged mantle 
showed only one anal fissure. In the middle of the ventral 
range lay a long corrugated cylindrical tubular foot, which 
appeared capable of great extension ; it made its way through 
the body to the branchiz, and there threw off vessels, mght 
and left, which appeared to communicate with those organs, 
so that it would seem that the foot performs both the functions 
of a locomotive, and is a vehicle to convey water to the 
branchize, in lieu of the usual posterior siphon ; and it is pro- 
bable that throughout the genus Lucina the foot performs this 
double duty. There is only one thick branchial plate, as in 
L. boxealis, doubled on itself, of a red-brown colour. No 
palpi were detected. The liver, formed of two minute leaf- 
shaped hght green granular masses, curiously lines the body 
and part of the foot on each side. 
This animal was taken in company with the L. borealis 
above described, close to the shore, at Straight Point, Little- 
ham Cove, near Exmouth. 
