534 TKOCHID.^. 



Berwickshire (Johnston) ; Fifeshire (E.F.) ; Aberdeensliire 

 (Macgillivray) ; very common among Laminariee in Orkney 

 (Thomas) ; Zetland (M'Andrevv) ; Skye (E. F.) ; Oban, 

 and elsewhere on the west coast of Scotland (Barlee) ; 

 Arran, in the Clyde (Alder) ; north east coast of Ireland 

 (W.Thompson). Its southernmost habitats are Dublin 

 Bay (Warren) and Tenby (Lyons). Abroad its range 

 corresponds to that of undulatus. 



T. pusiLLus, Jeffreys. 



Minute, suborbicular, perfectly smooth, semi-transparent : um- 

 bilicus narrow, longitudinally grooved at its commencement. 



Plate LXXIII. f5g. 3,4. 

 Margarita pusilla, Jeffreys, Ann. Nat. Hist. vol. xx. p. 17. 



Although we entertain not the slightest suspicion of this 

 minute shell being the fry of either Helicinus or undulatus^ 

 each of which, even in its earliest stage, exhibits spiral lines 

 upon its base, it is nevertheless possible that this species 

 may hereafter prove to be the young of some other northern 

 shell not hitherto taken in our waters. 



It is excessively thin, semi-transparent, shining, sub- 

 nacreous white, or amber-coloured, and of a somewhat 

 globosely orbicular form, with the anterior end of the 

 aperture projecting considerably below the basal level. 

 The general surface is quite smooth, yet, upon some of 

 the larger specimens, there seem faint traces of longitudinal 

 wrinkles. There are three convex whorls, that are neither 

 depressed nor flattened, well-marked near the suture, and 

 are much less shelving above than in Helicinus. The body, 

 which is extremely ample in proportion, is ventricose, and 

 broadly rounded at the circumference ; the penult volution 



