122 



CYPRINID^. 



Fig. 433. 



A. semisulcata. 



Venus boreaUs, Chemn. Conch, vii. t. 39, fig. 412. 



Crassina horealis, Xills. Nov. Act. Holm. 188 (1822), t. 2, figs. 3, 4. 



Aatarte cyprlnokhs, Duv.\l, Rev. Zool. 278 (1841). — Haxley, Recent Shells, Suppl. 



t. 14, fig. 40. 

 V<nus coiiiprcssa, Montagu, Test. Br. Suppl. t. 26, fig. 1. 



Astarte coin/irrssa, McGim.iy. Moll. Aberd. 261. — Thokpe, Br. Mar. Conch. 247. 

 CrissiiKi coiit/n-ssa, Brown, III. Conch. G. Br. 96, pi. 38, figs. 4, 5. 

 Ciassimi coiriii/iitit, Bkown, ibid. 96, t. 40. fig. 24. 

 Aslarte corruyata, Loven, Ind. Moll. Scand. 37. 

 A^tarte lactta, Gould, Inv. 1st. ed. 80, fig. 47. 



Shell orbiciilar-elliptical, rather thin, much compressed ; surface 

 marked with rather remote, romided, rib-like ridges, most conspic- 

 uous along the })Osterior slope of the disk ; 

 covered with a dark yellowish-brown epider- 

 mis ; beaks nearly central, elevated and in- 

 clined forwards, with a short, lanceolate lu- 

 nule in front, and a longer corselet behind, 

 both of them deeply excavated ; the anterior 

 slope from the beaks is concave for a very 

 short distance, the posterior is straight, and 

 both extremities are broadly rounded, the an- 

 terior most so ; ligament broad ; hinge-margin narrow and rather 

 feeble, and cardinal teeth slightly elevated ; on one side is a tooth- 

 like ridge along the margin, and on the other a groove to receive 

 this ridge ; in the right valve the groove is before, and the ridge 

 Ijehind the cardinal teeth ; cavity of the valves rather shallow ; mus- 

 cular and pallial impressions rather indistinct, except in old speci- 

 mens ; the margin is sharp and not crenulated. Length, one and 

 one tenth of an inch; height, one inch; breadth, two fiftlis of an 

 inch ; a large specimen, one and three fourths of an inch, one and 

 throe eighths of an inch, five eighths of an inch. 



This shell, from the cabinet of Colonel Totten, was brought from 

 the Grand Bank. Of the two specimens, one is about half the size 

 of the other. Nova Scotia ( WWis) ; Port Foulke {Haz/cs Coll.). 



Tlie specimen from the Arctic Seas, figured in the " Apjjendix to 

 Beechey's Voyage," is much larger than either of these. 



It is distinguished from A. sulcata by its broadly rounded extrem- 

 ities, compressed form, delicate and short ridges, slender hinge, 

 shorter impressions each side of the beak, and its probably plain 



margin. 



[It differs from A. lactcn, for which I mistook it in the former 

 edition, in having the outline of its internal face almost ])rccisely 

 egg-shaped, except in young specimens, where there is a short and 



