432 MR. E. A. SMITH ON SHELLS FROM ADEN. [June 16, 



name, printed A. uropigimelana in Encyclop. Method. Vers, plates 

 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. 



Hub. Philippine Islands ; Gulf of Suez (CooJce). 



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 costae. 



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 (LamJc.). 



254. CucuLLiEA concamerata (Martini). 

 Hab. Indian Ocean (various parts), China. 



255. Pectunctjlus pectunchlus (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. ed. 2, 

 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 costse 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 {Gvi?i\i\Qr, Test. pi. 72. f. H, and ? Argenville, 

 Conch, t. 27. f. B) represent a species the ribs of which are sepa- 

 rated by very narrow sulci. This same form is figured by Reeve 

 (Conch. Icon. ff. 11 a, 116), Chemnitz (Conch.-Cab. vii. ff. 568-9), 

 Crouch (Conch, pi. 8. f. 12), Knorr (Vergniigen, v. pi. xii. f. 4), 



