374 TELLINID^. 



and contiguous ; umbones projecting, but not disproportion- 

 ately convex : lunule deep, lanceolate, elongated, and of a red- 

 dish-brown hue : ligament long, rather prominent, dark horn- 

 colour : hinge-line curved : hinge-plate thick, broad, and flexu- 

 ous : teeth similar to those in T. balaustina, but stronger ; the 

 anterior lateral in the right valve is very large and conspi- 

 cuous : inside highly glossy and nacreous, longitudinally marked 

 towards the margin with faint and indistinct lines, and some- 

 times streaked irregularly from the hinge to the centre with 

 bright pink or rosecolour : pallial scar well denned, large, ex- 

 tending across nearly to the anterior adductor muscle, and 

 slightly lineated in the same direction : muscular scars deep, 

 particularly that of the anterior adductor, which is pear- 

 shaped. L. 1-8. B. 2-1. 



Yar. albida. Shell whitish and without coloured rays. 



HABITAT : All our sandy coasts, from the Shetland to 

 the Channel Isles, from low-water mark to 55 fathoms. 

 Var. 1. Lerwick (Barlee and J. G. J.). This species is 

 fossil at Ayr ( J. Smith), and in the Mammalian, Bed, and 

 Coralline Crag (S. Wood). Nyst has recorded it from 

 the Belgian Crag, and Philippi from the Sicilian upper 

 tertiaries. It is not uncommon in the North Sea from 

 Drontheim (Sars) to the Bohuslan district (Loven and 

 Malm), and south of Great Britain from Normandy 

 (Bouchard-Chantereaux) to Gibraltar and the Gulf of 

 Tunis (M'Andrew and Deshayes), at depths varying from 

 8 to 35 fathoms. 



Turton noticed that one of the valves is more convex 

 than the other ; the inequality is not great, but very per- 

 ceptible. Independently of this character, and of its 

 being infinitely more common, T. crassa differs from 

 T. balaustina in being at least six times the size, having 

 a more solid texture, and the ridges being stronger and 

 more compact ; the fry are oval instead of triangular. 

 The one is the "porcelain of creation"; the other is 

 common ware. 



According to Brown, the present species is the type 



