242 LUCINID^. 



orange tint, and their delicate flounces almost equalling 

 the ornamentation of the once-prized Venus Dione. The 

 fry are quite smooth and glossy. 



This constituted the type of Turton's genus Myrtea, 

 and of Leach's genus Cyrachaa. It is the Venus hia- 

 telloides of Delle Chiaje; and Philippi at first adopted 

 that specific name, not being aware that the species had 

 been long previously described by Montagu. Macgilli- 

 vray considered it to be only the young of L. borealis ; 

 but it may be readily distinguished from that shell by 

 its shape, which is triangular instead of circular, by its 

 beaks being much less prominent, and by the row of sharp 

 spines on the dorsal margin. 



2. L. borea'lis *, Linne. 



Venus borealis, Linn. Syst. Nat. p. 1134. L. borealis, F. & H. ii. p. 46, 

 pi. xxxv. f. 5, and (animal) pi. M. f. 6. 



Body clear white : mantle open from the anterior adductor 

 to near the posterior muscle, where it is contracted and nearly 

 closed : labial palps one on each side of the mouth, short, coarse, 

 thick, nearly cylindrical, and striated : foot placed in the middle 

 of the ventral area, very narrow, and lancet-shaped at the ex- 

 tremity. 



Shell roundish, more or less tumid, solid and opaque, of a 

 dull chalky hue : sculpture, numerous concentric ridges or 

 ribs, which are not much raised although tolerably sharp ; they 

 become closer, irregular, and even confluent towards the front 

 margin in adult specimens, and are somewhat laminar towards 

 the posterior margin ; the only other markings appear to be a 

 few slight and minute concentric lines between the ridges : 

 colour white : epidermis rather thick, fibrous, puckered, and 

 light yellowish-brown : margins obliquely truncate on the an- 

 terior side, and forming nearly a right angle with the dorsal 

 margin in consequence of the line from the beaks along the 

 lunule being almost straight, rounded in front, with a slight 

 tendency to obliquity, and somewhat truncate on the poste- 



i 

 * Northern. 



