PYEAMIDELLID^3. 405 



been the arena and one of the great laboratories of the species- 

 manufacturers, who have turned them out with a liberal hand. 

 This has in some measure been occasioned by the singular 

 variations exhibited by the individuals of almost every species 

 of the genus. 



I here offer a correction. When I stated in the ' Annals of 

 Natural History ' that all the Chemnitzia had a similar apo- 

 physis in the operculum to that assigned by Mr. Alder as one 

 of the distinguishing characters of the genus Jeffreysia, I 

 thought my discovery a new one ; but I find by Dr. Johnston's 

 excellent ' Introduction to Conchology/ from a paper inserted 

 therein, written in 1835, by John Edward Gray, Esq., that 

 that gentleman is the original discoverer of the flap or 

 process in the opercula of the Pyramidellidae. I now pre- 

 sent a most important quotation from that portion of the 

 paper relating to the opercula (p. 449) ; Mr. Gray says, 

 " The opercula of some shells which have plaits on their pillar 

 are very thin, and are furnished with a moveable flap on the 

 left side of their anterior margin, which passes over the plaits. 

 I first observed this in the common Tornatella, and after- 

 wards in Turbo pallidus of Montagu, the genus Odostomia 

 of Dr. Fleming, and have since verified it in Pyramidella. 

 The subannular operculum of Turbinella cornigera has a 

 notch in the middle of the anterior margin and a plait 

 running from the nucleus, but in this case the flap is not 

 moveable." 



The latter part of Mr. Gray's remarks with reference to the 

 subannular operculum, the plait running from the nucleus, 

 and the flap not being moveable, precisely embrace my views 

 of Jeffreysia diaphana, in which the flap, as Mr. Gray calls it, 

 is not moveable ; and I found that to be the case in most of 

 the fourteen species of Chemnitzice I have examined ; but in 

 some, for instance the young shells of Chem. pallida, and in 

 Chem. rufa, the flap or apophysis is moveable, or in other 

 words, it is cartilaginous and flexible. 



The aspect of the Chemnitzian animal is so peculiar and 

 impressive, that when once it has been seen it will never be 

 forgotten, and the malacologist will instantly detect an indi- 



