154 limn^ad^e. 



Helix carinata, Mont. Test. Brit. p. 451, pi. 25, f. 1. 



„ planata, Maton and Rack. Trans. Linn. Soc. vol. viii. p. 189, pi. 5, f. 14. 

 —Dorset Catalog, p. 52, pi. 20, f. 18.— Wood, Index Testaceolog. 

 pi. 33, f. 23. 

 Planorbis lutescens, Jeffr. (not Lam.) Trans. Linn. Soc. vol. xvi. p. 385, changed 

 to disciformis, p. 521 (from type). 

 „ planatus, Turt. Manual L. and F. W. Shells, p. 110, f. 92. 



Shell of an ashy horn-colour, moderately depressed, the 

 height to the breadth being usually as one to five, more 

 or less translucent, much shining, smooth, or nearly so. 

 Upper disk rather deeply concave in the middle, lower 

 disk flat. Whorls five, deeply divided, of rapid increase, 

 simply rounded on the right disk, convex on the left one. 

 Body decidedly broader than high, more especially on the 

 upper disk, where it is peculiarly large in proportion to the 

 preceding turn (so that a line drawn across it at one-third 

 the circumference from the aperture is more than equal to 

 the diameter of the remaining coils) ; encircled below the 

 middle, but above the level of the lower disk, by a project- 

 ing keel-like rim, above which the rounded surface does 

 not arch simply to the edge, but shelves towards it. Mouth 

 somewhat rhomboidal, broader than high, rounded above 

 and below, angulated laterally. Outer lip acute, projecting 

 a little above the upper level, and only slightly disposed to 

 expand there, scarcely extending beyond the lower level. 

 Breadth half an inch. 



In the variety disciformis the middle of the lower disk 

 is almost convex, and the keel in consequence seems more 

 central. 



The animal is of a pale translucent yellowish hue, dark- 

 ening to brown. 



This is a local species, but widely diffused in England, 

 and occurring in scattered localities in all our districts, pro- 

 bably becoming more common towards the east and south- 



