216 ARCADE. 



Glycimeris argentea, Da Costa, Brit. Conch, p. 170 (in part), pi. 15, f. G (on 



the right). 

 Nucula margaritacca, Lamarck, Anim. s. Vert. (ed. Desh.) vol. vi. p. 50(i 

 (chiefly). — Brown, Illust. Conch. G. B. p. 85, pi. 33, 

 f. 12. — Philippi, Moll. Sicil. vol. i. p. 64, and vol. ii. 

 p. 45. 

 „ nucleus, var. /3. Loven, Index Moll. Skandinav. (from specimens). 



This very abundant species (at least to the dredger, for 

 it is rarely thrown perfect upon the shore) is of a shortened 

 subtriangularly ovate form, seldom oblique, moderately con- 

 vex, strong in texture, and covered with a dull olivaceous 

 yellow, or ashy-olive coloured epidermis, the surface be- 

 neath which is of an uniform white, and entirely devoid of 

 any coloured rays. The exterior is almost smooth in the 

 middle, and on the umbones, but at the sides and base is 

 marked with very faint radiating strisc, which are occasion- 

 ally obscurely decussated by rather strongly marked lines 

 of growth and slightly elevated wrinkles. The ventral 

 edge is moderately arcuated, and rises rather the more in 

 front ; the hinder dorsal edge slopes with but little con- 

 vexity, and uniting with the ventral without angulation 

 forms a somewhat tapering and bluntly rounded termina- 

 tion to the produced posterior side. The front margin does 

 not abruptly decline (although the anterior side is still very 

 short) in a straight line, but is sinuous, a very obscure 

 emargination terminating it below, above which it swells 

 out a little, so as to give a sort of pouting appearance to 

 the lips of the lunule. This latter, which is only defined 

 by a slight retusion of the surrounding surface and the 

 absence of radiating striulee, is large and destitute of sculp- 

 ture. The hinder dorsal area is a little flattened, and its 

 lips bend inward ; it is likewise devoid of all sculpture, or 

 marked characteristics. The umbones are not peculiarly 

 prominent, nor are the beaks, which curve forward, very 



