274 MALACOZOA. TROPIOFODA. LAMELLIBRANCHIATA, 



Very young individuals are nearly orbicular, with the epi- 

 dermis transparent, the colour of the shell white or reddish- 

 white, beautifully spotted or patched with red. 



Apparently very rare. I have found only one very small, 

 finely variegated specimen, which was brought up by a fish- 

 ing-line, from the Bay of Aberdeen. 



Cardium lsevigatum. Linn. Syst. Nat. i. 1123? — Cardium laevi- 

 gatum. Turt. Brit. Biv. 190. — Cardium lgevigaturn. Flem. Brit. 

 Anim. 423. — Cardium lffivigatuin. Mont. Test. Brit. 80. — Car- 

 dium serratum. Lamk. Syst. vi. 11; Ed. 2. vi. 401. — Cardium 

 lsevigatum. Penn. Brit Zool. iv. 91. PL 51. f. 40. 



6. Cardium elongatum. Oval Cockle. 



Shell ovato-orbicular, somewhat oblique, compressed ; with 

 the dorsal margin nearly straight, and about twice as long as 

 the frontal ; the anterior end rounded, the posterior subtrun- 

 cate ; the valves thin, with twenty-six close convex ribs, echi- 

 nate, especially toward the margins, with direct, thin, pointed 

 spines ; the colour yellowish- white, with some faint reddish 

 markings. Length a twelfth of an inch, height a sixth less. 



This beautiful species differs from the young of Cardium fas- 

 ciatum, in having the dorsal margin much longer, the ribs 

 more numerous, the prominences upon them not in the form 

 of transverse lamellae, but of short, thin, pointed spines. 



Found by me among shell sand, from the Bay of Cruden, 

 sent by Mr. Alexander Murray, in November, 1842. The 

 description is from a single individual of small size. Montagu 

 says it attains a quarter of an inch in diameter. 



Cardium elongatum. Mont. Test. Brit. 82. — Cardium elonga 

 turn. Turt. Brit. Biv. 185. — Cardium elongatum. Flem. Brit. 

 Anim. 422. 



Genus 2. Donax. 



Animal oblong or subtrigonal, compressed. The lobes 

 of the mantle very thin, disunited in front and beneath, 

 with the margins fringed with tentacular appendages, 

 united behind, but forming an orifice for the tubes, 

 which are separate and elongated. Mouth small, with 

 large labial appendages. Branchiae very unequal. Foot 

 compressed, thin-edged, angulate. Adductor muscles 

 large. 



Shell more or less triangular, compressed, regular, 



