PAKDOKA. 151 



tumid than the right: the mantle is closed, except a small 

 fissure at the anterior end for the issue of the foot ; posteriorly 

 it forms a sheath, which encloses the very short, scarcely 

 separated siphons, that merely show their extremities, which 

 are fringed at the orifices with fine white short cirrhi ; the 

 margin of the sheath, in some specimens, is marked with a fine 

 orange line, and the base of the cirrhi and margins of the ori- 

 fices are usually encircled with a dead-white narrow thread. 



With regard to the branchiae, I have great satisfaction in 

 stating, that after the examination of many live specimens, I 

 am enabled to settle the true character of them. I have been 

 most anxious on this head, as the statement in the ' British 

 Mollusca/ pp. 210-212, is given from old notes of mine in 

 1835, in which it is observed, that there are two palpi and 

 one branchial lamina. Later and repeated examinations 

 require the following rectifications. I can now say, beyond 

 dispute, and show the fact by preparations, that there are two 

 palpi and two branchiae on each side of the body ; the branchise 

 run horizontally, being long, narrow, slightly arcuated, and 

 symmetrical, pale brown, and pectinated by the blood-vessels 

 on both surfaces ; their posterior points pass into the branchial 

 tube; the palpi are short, small, pale brown, triangular, pointed, 

 and striated transversely. The ovarium is orange-coloured, and 

 placed posterior to, and in contact with, the dark green liver : 

 in the genial months the ova, in all stages of development, are 

 very conspicuous, which, we think, on exclusion pass, without 

 any delay in the branchise, into their native element. The 

 intestine passes out of the posterior basal part of the liver to 

 the bottom of the body, and then ascends under the branchiae 

 and adductor muscle to its termination in the anal tube. 



This very elegant species, both as to the animal and shell, 

 is sufficiently plentiful, alive, at Exmouth, in the coralline 

 zone. 



P. ROSTRATA, Lamarck. 

 P. rostrata, Brit. Moll. i. p. 207, pi. 8. f. 1-4. 



This species is an inhabitant of the Channel Islands ; we 

 believe there is no well-authenticated capture of a live animal 

 on the strictly British coasts. 



