294 BUccixiD.E. 



periphery ; edge in full-grown specimens reflected ; inside 

 smooth : inner lip imperceptible, consisting merely of a slight 

 glaze which imparts a polished appearance to that side : pillar 

 microscopically pustulated : operculum very small, triangular, 

 with a rounded outline, not very thin, somewhat concave;' 

 lines of growth fibrous and close-set. L. 1*75. B. 1. 



Yar. lactea. Milk-white. 



Habitat: The outer '^haaf''^ or fishing-banks^ east 

 and north of the Shetland Isles, in 73-90 f. ; also in 

 Vidlom voc on the mainland of Shetland, 18 f. (Nor- 

 man) ; Hebride's (Forbes, M'^ Andrew, and Barlee) ; co. 

 Cork, 40 f. (Humphreys and Armstrong) ; Connemara 

 (Professor King) . ? Fossil in Palermo and Calabria 

 (Philippi, as B. striatum). Living in Manger fiord 

 (Sars, mus. Christ.). The shells received by the late 

 Mr. G. B. Sowerby fi'om Newfoundland, and referred 

 by him to this species, appear to be B. Grcenlandicum ; 

 and the same remark applies to those recorded by Pro- 

 fessor Geikie from the Clyde beds. Dr. Stimpson must 

 have mistaken some other species (perhaps B. ciliatum) 

 for B. Humphrey sianum when he described the latter 

 as having a ciliated epidermis ; and I therefore cannot 

 recognize the North American localities indicated by 

 Him. B. ventricosum of Kiener (from the coast of Pro- 

 vence) is closely allied to our shell ; but the whorls are 

 more tumid and gibbous, and the operculum is not so 

 disproportionately small. They bear the same relation 

 to each other as Aporrhais Serresiana does to A. Mac- 

 andrecB. 



This shell diff'ers from the variety Zetlandica of B. 

 undatum in its more regularly oval shape, thinner tex- 

 ture, much finer sculpture, entire absence of an epi- 

 dermis, not having a basal keel or an inner lip, and in 

 its extremely small and triangular operculum ; from all 



