THE LAND AND FRESHWATER MOLLUSCA OF DORSETSHIRE. 89 



7. P. COMPLANATUS, Linn., pi. 6. 



P. MARQINATUS, F. and H. iv., p. 155, pi. cxxvii., f. 1 3. 



HELIX PLANORBIS, Pult. cat., p. 46, Rack, ed-, p. 52, pi, 14, f. 8, 

 and pi. 20, f . 1 0. 



Shell rather concave above, and slightly convex below, smooth, 

 slightly glossy, not so transparent as the last, yellowish horn-colour 

 with sometimes a tinge of brown ; whorls six, deeply divided, 

 rounded on the upper part, convex on the lower; periphery with a 

 carinated rim, which rises barely above the basal level : breadth of 

 body whorl at>out a quarter of th. shell; mouth rounded-oval, angu- 

 lated laterally by the keel, the inside sometimes furnished with a 

 rib; umbilicus broad and very slvtllow. L. 0.1^5. B. 0.6. 



The shell of P. comj>lanatns differs from that of P. carinatus by 

 the whorls being more rounded, the keel placed on the lower side 

 instead of the middle of the periphery. 



Hab. Marshes, canals, ponds, and standing water. River 

 Stour, Bryanston ; Chamberlayne's meadows, Bere Regis ; Sto- 

 borough meadows, Warehajn (J.C.M.P.). 



8. P. COKNEUS, Linn-.* pi. 6. 



HELIX COKNEA, Pult. cat., p. 47, Rack, ed., p. 52, pi. 20, f. 13. 

 Mont. rest. Brit., p. 448. 



Shell very concave above, nearly fl it bolow, with well defined 

 longitudinal, irregular flexuous striae, which are met at right angles 

 by others equally fine on the surface of the first whorls, smooth, 

 glossv, whitish horn-colour with a reddish brown tinjre; whorls five 

 to six. the last dilated towards the mouth, diameter of the last whorl 

 rather less than one-third of the whole shell ; suture deep ; mouth 

 very large, the upper border rather projecting ; umbilicus shallow. 

 L. 0.35. B. 1. 



Hab. Slow streams, ponds and ditches. It is the largest of 

 the other European species afPlanjrKt. When irritated it sends 

 forth a quantity of red-coloured liquid. " Plentiful in some 

 parts, though we have not found it further westward than Dor- 

 setshire ; about Wareham it is abundant'' (Montagu). 



9. P. CONTORTUS, Linn., pi. 6. 



HELIX CONTORTA,PW^. cat., Rack, ed., p. 53. pi. 20, f. 11. 



flhell slightly depressed above, concave towards the centre as 

 well as below, dark or brown horn-colour, opaque ; whorls from six 



