THE LAND AND FRESHWATER MOLLTJSCA OF DORSETSHIRE. 85 



2. B. LEACHII, Sheppard, pi. 6. 



Body greyish-white with black and yellow specks. 



Shell conical, ventricose towards the base, with indistinct longi- 

 tudinal striae, thin, glossy, sub-transparent, yellowish horn-colour ; 

 whorls five, very convex, the last occupying about one-half of the 

 shell; suture deep ; spire bluntly pointed ; ttmbilicus scarcely more 

 than a slit ; mouth nearly round, slightly angular above ; outer and 

 inner lips uninterrupted ; operculum with distinct concentric striae, 

 the exterior of a darker hue, edges raised. L.0.25. B.0.2. 



Hab. Slow rivers, ponds and watercourses. Holwell (Rev. 

 H. H. Wood). 



Genus III.HYDROBIA, Hartmann. 

 Forms an intermediate link between Bythinia and Rissoa (marine). 



1. HYDROBIA VENTROSA, Montagu, pi. 6. 



TURBO VENTROSUS, Pult. cat., Rack. ed. p. 49, pi. 18, f. 12a. 

 Body dark grey, almost black in front. 



Shell smooth, glossy, and thin, yellowish horn colour, six to seven 

 ventricose whorls ; apex pointed ; outer lip slightly reflected ; 

 operculum oval, thin, and flat, resemoling that of the marine genus 

 Littorina. L.0.2. B.0.125. 



Usually lives in ponds, and ditches into which the sea only 

 flows at high water or spring tides. Weymouth, adhering to 

 Ulva lactuca, T. Rackett ; River Frome, Wareham, below 

 Redcliff(J.C.M.P.). 



2.* SIMILIS, Lraparnaud, pi. 6. 



EISSOA ANATINA, F. and H. ii., p. 134, pi. Ixxxvii., f. 3, 4. 



Body dark grey, with a yellow or brown tint and white flakey 

 specks. 



Shell oval, ventricose, rather thin, pale horn-colour, sometimes 

 whitish, with fine longitudinal striae ; whorls convex, from four to 

 five, the last occupying more than two-thirds of the shell ; spire 

 rather pointed ; umbilicus a mere narrow chink; outer lip thin, 

 reflected, continuous with the inner lip operculum thin, flat, marked 

 with irregular, flexuous lines of growth. L.0.15. B.O.I. 



Hab. Muddy ditches, which are occasionally, but seldom 

 overflowed by the sea. Watercourses adjoining the Chesil- 

 Bank at Abbotsbury and at Bexington (J.C.M.P.). 



