LITTORINA. 27 



appropriate enougli, for there is a comparative flattening 

 of the ventral or underneath portion of the body whorl, so 

 that an horizontal section, as in the genus Nerita^ would 

 be somewhat hemispherical. 



The shape ranges from ovate-conic to oval-conoid, and 

 the colouring, in our native specimens, whose hue is for the 

 most part uniform, or only diversified by a single narrow 

 basal zone of a whitish cast, from purplish brown to cho- 

 colate black ; in the Mediterranean examples the tint is 

 more frequently bluish grey passing into ashy v/hite near 

 the sutures and the base. The shell is rather thin, but 

 not transparent ; when in fine condition it is almost smooth 

 (or with a few wrinkles of increase), and somewhat glossy, 

 but from the ordinary exposed nature of its habitat on 

 the British coast, is generally dull and eroded. The spire 

 is merely composed of four short and much shelving- 

 volutions, that quickly slope to a tolerably acute point, 

 and are divided from each other by a fine suture ; although 

 not ventricose, but merely convex, or even flattened, they 

 are well defined. The body occupies from two-thirds to 

 three-fourths of the entire length, the former proportion 

 in the more produced specimens, the latter in the more 

 abbreviated ones ; its surface is not simply rounded, but 

 flattened and shelving towards the suture, and upon the 

 basal portion of the ventral or underneath side of the 

 shell. The mouth occupies from one-half to two-thirds 

 of the entire length ; it is subpyriform, or oval-acute, 

 rounded below, and contracted above to an acute angle. 

 The two lips are connected by a broadly spread enamel, 

 that is usually of a reddish-liver or chocolate colour ; the 

 outer lip is peculiarly sharp-edged, and disposed to expand, 

 especially at the broadly rounded base. The pillar is 

 wide, flat, and bevelled to a sharp edge (which is occa- 



