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 branchiae from 

 the ventral range. There is certainly 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,' pi. M. f. 6. 



This species is the type of the genus. 



L. FLEXUOSA, Montagu. 



L.flexuosa, Brit. Moll. ii. p. 54, pi. 35. f. 4. 



Exmouth, 2nd June, 1852. 



Animal inhabiting a white, irregularly globular shell, Avith 

 a longitudinal posterior furrow. It was apathetic, and pro- 

 truded no organs. On being 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 branchiae, and there threw off vessels, right 

 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 

 branchiae, 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. boygalis, doubled on itself, of a red-brown colour. No 

 palpi were detected. The liver, formed of two minute leaf- 

 shaped light 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. 



