88 THE LAND AND FRESHWATER MOLLUSCA OF DORSETSHIRE. 



4. P. SPIRORBIS, Miiller, pi. 6. 

 HELIX SPIRORBIS, Pult. cat., Rack, ed., p. 53, pi. 20, f. 17. 



Shell rather concave above, flat below, fine and irregular longitu- 

 dinal striae, very thin, smooth and glossy ; brown horn-colour ; 

 periphery angular, slightly keeled below ; whorls five to six. the 

 last the largest, which is slightly dilated on approaching the open- 

 ing; month somewhat rounded, often strengthened inside by a rib ; 

 inner lip continuous with the outer lip ; umbilicus large and shallow. 

 L.0.04. B.0.25. 



Hab. On plants and grass in shallow water. Generally dis- 

 tributed. 



5. p. VORTEX, Linn, pi. 6. 

 HELIX VORTEX, Pult. cat., p. 47, Rack, ed., p. 52, pi. 20, f. 12- 



Shell compressed, concave above, flat below, thin, glossy, yellow- 

 ish or greyish horn-colour, thin, fragile, slightly glossy and trans- 

 parent, with closely set, unequal, flexuous lines of growth ; whorls 

 si's to eight, slightly convex above, each succeeding one scarcely 

 exceeding the other in dimensions : suture well marked above; keel 

 well denned ; mouth small, angular above, an 1 like the preceding, 

 the inside is sometimes thickened by a slight rib; umbilicus large 

 and shallow. L.0.05. B.03. 



Hab. Similar to that of P. spirorbis. River Stour, Spettis- 

 bury ; river, Chamberlayne's, Bere Regis (J.C.M.P.). 



6. P. CARINATUS, Miiller, pi. 6. 



HELIX PLANATA, Pult. cat., Rack, ed,, p. 52, pi. 20, f. 18. Brit' 

 Conch., vol. i., p. 90. 



Shell concave above, slightly so below, striae rather indistinct, 

 very fine and arched, thin, glabrous and rather glossy, very trans- 

 parent, yellowish horn-colour; whorls five to six, the last much the 

 largest and dilated towards the mouth, which is oval; periphery 

 sharply keeled in the centre, from which it gradually slopes both 

 above and below ; suture deep; mouth obliquely oval, rounded above 

 and below, angulated laterally, the inside not furnished with a rib ; 

 outer lip continuous with the inner lip. L.O.I. B.0.5. 



Hab. Marshes and stagnant water. River Frome, between 

 Wareham and Stoke ; Woolbridge -, Chamberlayne's, Bere Regis 



(J.C.M-P.;. 



