360 PLEUROTOMATID.E. 



G. J.^ M ^Andrew and Forbes^, and Barlee) ; Orkneys 

 (Thomas_,^^^e F. & H.). Finmark (Loven); Cliristian- 

 sund, 30-40 f. (Lilljeborg); Upper Norway (M^ Andrew 

 and Barrett) . 



It is variable in size. We do not know the exact 

 position, in a generic point of view, of this delicate little 

 shell. In 1841 1 named it Fusus albus. The Pleurotoma 

 nanum of Scacchi is a very different species. Our shell 

 is allied to C. HoIboUii ; but that has a small shield-like 

 operculum, and is longitudinally ribbed at the top. 



The last-named species is one of our glacial fossils ; 

 it has been dredged by Mr. AYaller, Mr. Ilyndman, and 

 myself on the Turbot bank, co. Antrim, in 20-25 f., by 

 Mr. Norman and myself in the Hebrides, at a depth of 

 60 f., and by Mr. Dawson off the Aberdeenshire coast. 

 I found it also in the Fort William deposit. It inhabits 

 every part of the Arctic seas, from Bergen, northwards, 

 and the United States. The late Professor Gould de- 

 scribed it as Bucclnum rosaceum. This species was 

 erroneously placed by Morch in the genus Mitrella (as 

 "MitseUa") of Risso. 



Family XXX. PLEUEOTOMA'TID.^, {Pleu- 

 rotomacea) Loven. 



Body spiral, more or less elongated : mantle forming a short 

 fold above the head for excretal purposes, the fold occupying 

 a fissure or notch in the outer lip of the shell : ixdUal tithe not 

 protruded much beyond the canal of the shell : Jiead small : 

 proboscis retractile : tentacles placed far apart, with slender 

 points : ei/es on the extremity of stalks, which are conj oined 

 with the lower portion of the tentacles, and placed outside 

 them : foot lanceolate, double-edged in front, with a pointed 

 tail : gills arranged in two unequal-sized plumes : odontojohore 

 having no central tooth [" rhachis edentula," Loven] ; pleurae 



