PILEOPSIS. '265 



hues of the rose. The Emarginulce present similar conditions. 

 This remark is of some value to confirm natural position. 

 The mantle thickens gradually from the vertex to the base, 

 and is coloured in different individuals white, or tinted with 

 pale pink, and is also bordered with a dull red fringe. The 

 head is an elongated, grooved, emargmate muzzle ; the tenta- 

 cula are yellow, long, tumid at the base, conically tapering as 

 in Patella, with eyes on distinct but not much raised emi- 

 nences at the external bases. The branchial apparatus consists 

 of a heart and one auricle, and a series of long pale brown 

 filaments, which spring from the base of the walls of the 

 cervical cavity, and do not present a compact plumose leaf. 

 The foot is tough, coriaceous and circular, with an anterior 

 puckered ruff, or upper skin, or sort of meutum. This leads 

 me to observe again on the fact mentioned on my authority 

 in the ( British Mollusca/ that the matrix, or part thereof, is 

 sometimes, perhaps always, detached, and deposited on the 

 neck of the foot, for further development of the ova, for some 

 time previous to being committed to take care of themselves. 

 The same phenomenon is observable in lanthina, which will 

 be fully spoken of hereafter ; and I will now add, that with 

 respect to the so-called rudimentary lamina, which is stated, 

 though I have never seen it, to be sometimes observed on the 

 foot of this species, that it probably has its origin in a com- 

 pressed mass of testaceous pulli in adherence with it. 



Our examples, being taken many years ago from oysters 

 brought into Exmouth by the French dredgers for the oyster 

 plantations at Lympstone, though fresh, were sluggish, and 

 did not enable us to complete the descriptive notes with all 

 the accuracy that was desirable. 



Calyptreea and this species are exceedingly rare on the 

 southern coasts, off Exmouth, but, thirty years ago, the 

 P. hungaricus were found in abundance in Torbay ; this is 

 not so now : their disappearance is probably owing to the 

 oysters being all dredged, or buried beyond extrication by 

 the shifting of the marine beds of shingle. Our supplies 

 from the Jerseymen's trawl vessels have long been cut off, 

 in consequence of the French and English governments, to 



