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Show 432 MR. E. A. SMITH ON SHELLS FROM ADEN. [June 16, name, printed A. uropigimelana in Encyclop. Method. Vers, vol. i. p. 156, and the figures on pi. 307. No description or locality is given in the work. As the identification of the species from the figure only is uncertain, I prefer to retain Reeve's name holoserica, the type of which is before me. Young specimens are not nearly so much produced posteriorly as the adult form represented by Reeve's figure. 251. ARCA (ANADARA) CLATHRATA, Reeve. Hab. Philippine Islands ; Gulf of Suez (Cooke). A single specimen from Aden, 43 millim. in length and 34 high, has three more ribs than the type figured by Reeve, and is not quite so long in proportion. Reeve describes the epidermis as "very finely bristly between the ribs." The shell figured, as is evident from the illustration, is entirely devoid of periostracum, and neither in two other specimens in Cuming's collection, nor in that from Aden, is it "bristly," but roughly laminated between the costse. 252. ARCA (SCAPHARCA) RUFESCENS, Reeve. Hab. ? With this species I unite A. disparilis, Reeve, which, according to Kobelt, occurs in China. The species is variable in form and the number of ribs. The type specimen, although not a very large shell, is evidently old and much thickened. 253. ARCA (TRISIS) SEMITORTA, Lamarck. Hab. Philippines, N. Australia ; Tasmania (Lamk.). 254. CUCULL^EA CONCAMERATA (Martini). Hab. Indian Ocean (various parts), China. 255. PECTUNCULUS PECTUNCULUS (Linn.). Arca pectunculus, Linn., part., Syst. Nat. ed. 10, p. 695 ; Lister, Hist. Conch, pi. 239. f. 73 ; Savigny, Descrip. Egvpte, Atlas, pi. x. f. 2. Pectunculus subauritus, Lamarck, part., Syst. Anim. p. 115. Pectunculus pectiniformis, Lamk. part., Hist. Anim. s. Vert. vol. vi. p. 494. Hab. Bengal (Lister). Suez Bay, Gulf of Akaba, Persian Gulf, and Madagascar (Brit. Mus.). What I believe to be two distinct species of Pectunculus have been confused by Linne, Lamarck, and others. The figures cited above depict a form with the radiating costae separated by grooves, well-defined and about half as broad as the ribs themselves. On the other hand, the rest of the figures quoted by Linne as illustrative of his Arca pectunculus (Gualtier, Test. pi. 72. f. H, and ? Argenville, Conch, t. 27. f. B) represent a species the ribs of which are separated by very narrow sulci. This same form is figured by Reeve (Conch. Icon. ff. 11 a, 11 b), Chemnitz (Conch.-Cab. vii. ff. 568-9), Crouch (Conch, pi. 8. f. 12), Knorr (Vergniigen, v. pi. xii. f. 4), |