THE NAUTILUS. 117 



ceed to give, so far as they relate to species about which there is any 

 difference of opinion. 



Dr. Dall's identifications of Risso's list of species of Jamima agree 

 with those given by me except for the following four species: 



• ^^sso'^ °a°ie. Dall's table (p. 115). Pilsbry's table (p. 105). 



{\) J. muscorum. minutissuna Hartm. P. miisconim Ij. 



(2) /. marginata. muscorum L. P. umbilicata Dr. 



C3) J. edentula. edentula Drap. B. obscurus Mull. 



(4) J. quinquelamellata. quinquedentata Born. P. cinerea. 



My reasons for the names given in the third column follow : 

 (1). J. muscorum. The identity of this shell is at first sight not 

 very clear. Risso refers to Drap., who (very badly), figures P. 

 minutissima under the name muscorum; but Risso's description does 

 not at all fit minutissima, nor does the size given. Bourguic^nat, who 

 examined the Risso specimens, refers them positively to the P. mus 

 corum of L., as understood at the present time, and the description 

 agrees Avith this species. Risso's specimens would fall in the form 

 " unidenfata," Risso describing it as with a very small posterior la- 

 mella. 



The evidence obtained by a careful study of the original work 

 therefore shows that Risso did not have P. minutissima. 



(2) J. marginata. Risso gives three references: " Drap. 61, 6, 

 iii, 36, 38. Feruss. 59, 475. Playf. 59, 9, iii, 23, 24," all of them' 

 pertaining to forms of muscorum L. " Playf." is not Playfair, as 

 might be supposed, but Risso's curious conception of the name 

 Pfeiffer ; the work referred to being Carl Pfeiffer's Systematische 

 Anordnungund Beschreibungdeutscher Land und Wasser-Schnecken 

 (1821). Pfeiffer is elsewhere referred to as " Pleyfel !" 



Risso says that the peritreme is provided with a long acute lamella 

 posteriorly on the right. This cannot be made to fit any form of 

 muscorum, but applies perfectly to umbilicata Drap.; and Bourguig- 

 nat referred Risso's specimens, which he examined, to that species. 



(3) /. edentula. This is described by Risso as with eight ivhorls , 

 toothless aperture, and ten mm. long, so it clearly is not Sphyradium 

 edentxlnm, as Dall supposes. It is obvious that the reference to 

 Draparnaud's P. edentula was an error. These and the other char- 

 acters given by Risso agree with Buliminus obscurus (Ena obscura), 



