BYTHINIA. 27 



species, rather solid, not very glossy, yellowish-green, banded 

 and striated as P. contectaj epider^nis thickish ; whorls 6|, 

 rather swollen, body whorl occupying fully one-half of the 

 length of the shell ; apex rather blunt ; suture deepish ; mouth 

 more oval than in the last species ; oicter Up somewhat thick, 

 slightly reflected ; iJiner lip forming with the other a complete 

 peristome ; imibilicus a mere chink ; opercuhim rather thick, 

 depressed lengthwise, striated as in the preceding species. 



Inhabits sluggish rivers, lakes, and canals in many 

 parts of England ; in Scotland it seems to be of rare 

 occurrence, but it has been " found at Find horn, in 

 the Moray Frith district." Brown, in his ' Recent 

 Conchology,' says it occurs in Ireland in a stream 

 at Newtownards, Co. Down. 



The shell of this species differs from that of the 

 last in being more elongated and thicker, in the 

 whorls being very much less tumid, the suture much 

 shallower, and the apex blunter ; the mouth too is less 

 circular. It is more active than P. contecta, and is exceed- 

 ingly prolific. Millet counted in the ovary of a female 

 no less than eighty-two fry of different stages of growth. 



Var. I. unicolor. — Shell bandless. Hertfordshire, Thames 

 at Richmond, B.C. 



Var. 2. atro-purpiirea. — Shell same shape as the normal 

 form, but of a black colour, which when viewed by transmitted 

 Hght is dark purple. In the canal at Pontypool (R. M. 

 Lloyd), J.C, Feb. 1874, p. 6. 



GENUS II.— BYTHINIA,'' GRAY. 

 Eyes sessile, placed at the base of the tentacles ; opercuiiun 

 testaceous, irregularly concentric, nucleus nearly central. 



The animals belonging to this genus differ from 

 those of the last in the following particulars : — They 



* Living in deep water. 



