DONAX. 333 



to yield the name to the Mediterranean species, not only 

 from its being almost universally so designated throughout 

 Europe, but likewise from there existing a slight balance 

 in its favour, on weighing the rival claims by the evidence 

 of the original synonymy and descriptions. 



The shape of our British species is oblong-cuneiform, 

 and the texture is always more or less firm ; although 

 most decidedly inequilateral, for its genus it is less so than 

 usual. Typically it is compressed, but certain solid and 

 gigantic specimens from Stornaway are convex or even 

 subventricose. The exterior is more or less glossy, and is 

 sculptured with fine rather closely set radiating simple 

 striae, which diverge rather widely towards the margin, 

 and do not extend to the front portion or the hinder area ; 

 these in many specimens (but not invariably) are decus- 

 sated by still finer irregular scratch-like concentric lines on 

 the hinder side. Beneath the shining epidermis, which 

 passes from a lighter or darker oil-coloured yellow, almost 

 into olivaceous, the surface is generally tinged with livid 

 lilac of different shades (more rarely being pure white both 

 within and without), sometimes uniform, but frequently 

 with two paler or even white central diverging rays pro- 

 ceeding from the beaks, with the lines of increase indicated 

 by deeper belts of a livid hue : internally the colour ranges 

 from white to the darkest violet. The ventral margin is 

 more or less sinuous, presenting a slight and often almost 

 imperceptible trace of retusion posteriorly, but bulging out 

 anteriorward ere it abruptly ascends at the obtusely round- 

 ed front extremity. The dorsal edges are nearly straight 

 (yet always sinuous in some trifling degree), and in ordinary 

 sized specimens the front one scarcely declines, and the hind- 

 er one but moderately ; the extent of declination increases, 

 however, in the young, and in the large variety we have 



