234 ARCADE. 



460 species. They range in time as far back as the 

 Silurian epoch. We regard Cucullaa and Byssoarca as 

 scarcely sections of the genus. 



A. TETRAGONA, Poli. 



More or less stained with brown ; umbonal ridge sharply angu- 

 lated : ligamental area rhomboidal. 



Plate XLV. fig. 9, 10, and (Animal) plate P. fig. 1. 



? Area tortuosa, Pennant (not Linn.), Brit. Zool. ed. 4, vol. iv. p. 97. 



„ Now* Mont, (not Linn.), Test. Brit. p. 139, pi. 4, f. 3. — Donov. Brit. 



Shells, vol, 5, pi. 158, f. 1, 2. —Couch, Cornish Fauna, pt. 2. 



p. 30.— Brown, III. Conch. G. B. p. 86, pi. 33, f. 1, 2, 3. 

 „ fusca, Donovan (not Brug.), British Shells, vol. v. pi. 158, f. 3 (not 4). 



— Mont. Test. Brit. Suppl. p. 51. — Turt. Conch. Diction, 

 p. 10 ; Dithyra Brit. p. 166. — Fleming, Brit. Anim. p. 397. 



— Couch, Cornish Fauna, pt. 2, p. 30. — Brit. Marine Conch, 

 p. 101.— Brown. 111. Conch. G, B. p. 8G, pi. 33, f. 4, 5. 



,, Irtragona, Poli, Test. Sicilia?, vol. ii. p. 137, pi. 25, f. 12, 13. — Turt. 

 Dithyra Brit. p. 166, pi. 13, f. 1. — Fleming, Brit. Anim. 

 p. 398. — Forbes, Malac. Monensis, p. 41, pi. 3. — Brit. 

 Marine Conch, p. 102. — Brown, 111. Conch. G. B. p. 86, 

 pi. 33, f. 20, 21.— Lam. Anim. s. Vert. (ed. Desh.) vol. vi. 

 p. 461. — Philippi, Moll. Sicil. vol. i. p. 57. — Hanl. Re- 

 cent Shells, suppl. pi. 19, f. 13. — Reeve, Conch. Iconica, 

 Area, pi. 15, f. 100. 

 „ imbricate, Dillwyn (not Brug.), Recent Shells, vol. i. p. 226 (chiefly). 

 „ Cardissa, Lamarck, Anim. s.. Vert. (ed. Desh.) vol. vi. p. 463. — Alder, 

 Cat. Moll. Northumb. and Durh. p. 79. — Delessert, Re- 

 cueil Coq. Lam. pi. 11, f. 14. — Hanl. Recent Shells, vol. i. 

 p. 153. 

 „ papillosa, Brown, Wern. Mem. vol. viii. pi. 1, f. 19. 



* The Area Now of Dr. Turton, with " chestnut bands crossing the valves 

 diagonally" (Conch. Diction, p. 9, and Dithyra Brit. p. 166. — Flem. Brit. Anim. 

 p. 397. — Brit. Marine Conch, p. 101), is not identical with this shell, but agrees 

 rather with the veritable Noa, (Poli, Test. Sicil. vol. ii. p. 128, pi. 24. — Desh. 

 Exp. Sc. Algiers, Moll. pi. 120, anatomy) of Linnams, whose description in the 

 "Museum Ludovicae Ulrica?" is reprinted verbatim by Maton and Rackett, in 

 their " Descriptive Catalogue of British Shells" (Linnsean Transactions, vol. viii. 

 p. 91). It is not indigenous. 



