TRIBE ARCACEA. 157 



* * Inner margin crenulated. 



A. Helbingii. Lam. 24. — A. Candida. Gmel. 33\\. — Z>. 

 V- 228.— Ch.f. 542.— W. t. 9.f. 7. Transverse, anteriorly pro- 

 duced, posteriorly truncated, Avliite under a scaly epidermis, with 

 longitudinal crenulated grooves, which are in pairs at the anterior 

 end : beaks approximated, margin gaping and somewhat crenu- 

 lated. 2. — Guinea and Brazil. — " Probably a variety of Ovata.'^ 

 Desh. 



A. ScAPHA, Lam. 25. — Cli. f. 548. Transversely oblong, 

 ventricose, thin, white with the umbones reddish and oblique ; 

 with from twenty-nine to thirty-four ribs, which are divided into 

 two portions by a groove, (which is narrow but almost as deep as the 

 spaces between the ribs,) and are narrow and prominent parti- 

 cularly on the anterior side. 5^— India ? — JV. Indies ? 



A. Antiquata. Lin. 1141.— D. p. 232.— Lam. 26. -W. t. 

 9./. \7.— Ch.f. 548.— £. t. 306./. 2.— Gual. t. 87. c Trans- 

 versely ovate, obliquely heart-shaped, thick, white, ventricose, with 

 numerous flattened ribs, which are transversely striated, unarmed 

 and the posterior ones bifid: anterior side slightly angulated: area 

 between the beaks not grooved. 2. .3. — Mauritius, Mada- 

 gascar, L^'C.'^ 



A. Rhombea. Bo7'n.— GmeL 3314.— D. 233. — Layn. 27 .— 

 Ch.f. 5o3.—E. t. 307 /• 3.— TF. t. 9. /. 19. Heart-shaped, nearly 

 as long as broad, gibbous, white covered by a brown epidermis, 

 with about twenty-six longitudinal transversely striated ribs, and 

 their interstices nearly smooth: beaks incurved and distant, the 

 area between them rhomboidal. 1^. . 1^. — W. Indies. — E. Indies? 



A. Granosa. Lin. \\A2.—D. p. 233.— Lam. 28.— W. t. 9. 

 f \8.—List. t. 241. f. 78. -Ch.f. 5o7.—K?wrr. 3. t. 4./. 2.— 

 Sow. G. — Reeve, t. 82. ,/'. 3. Heart-shaped, nearly as long as 

 broad, very venti'icose, thick, almost equilateral, with upwards of 

 twenty rounded ribs, armed with orbicular, somewhat spinous 

 nodules, white within, and without, tinged slightly -with brown at 

 the beaks, which are incurved and rather distant with the area 

 between them covered with a dark brown ligament, marked with 

 rhomboidal grooves. 1#. . 2. — Indian Ocean. 



A. Auriculata. Lam. 29.— Del. t. 11. /. 12. — Savig. 

 Egy]t. t. lO./. 8. Heart-shaped, ventricose, white, under a hairy 

 epidermis, with about twenty-eight strong radiating crenulated 



* Deshayes separates as confounded with this, a species which I 

 propose to name in honour of that laborious savayit, A. Des- 

 viK\KS\\. — Glial, t. 87. B.—E. t. 306./ 1. Oblong, rather thin, 

 with rounded ribs and the area between the beaks marked with 

 lozeoge-shaped grooves. 



