Boone, Mollusca, Cruises of "Ara" and "Alva" 317 



Variety zanzibarensis Jameson, found on the east coast of 

 Africa, Zanzibar, Madagascar, Amirante Islands, Bazaruto Is- 

 lands, Mauritius, Rodriguez, Seychelles. 



Variety persica Jameson, found in the Persian Gulf, especially 

 in the fisheries of the Island of Bahrun and known to the trade as 

 "Bombay shell" because it is usually shipped via Bombay. 



Variety erythraensis Jameson, from the Red Sea. 



Variety cumingi (Reeve), the "black-edged shell" of eastern 

 Polynesia, found in Tahiti, Gambler Archipelago, Lord Hood 

 Island, Penrhyn Island and generally distributed in the islands of 

 eastern Polynesia, Galapagos Islands and Payta, Peru. 



Variety Tnazatlayiica Hanley, the "Panama shell" of trade, 

 known from the tropical and subtropical west coast of America 

 from the Gulf of California, especially Mazatlan and Angel de la 

 Guardia, also Panama and down to Payta, Peru. 



The species Pinctada galtsoffl Bartsch, from the Hawaiian 

 Islands, from the Pearl and Hermes Reefs and islands of Maui, 

 Oahu and Hawaii, is merely a colour variety of P. margaritifera 

 (Linne), long well known from this archipelago. 



Material examined : One specimen, collected by the "Alva" 

 at Falcon Island, Palm Islands, Queensland, October 7, 1931. A 

 single young specimen, of the variety cumingi Reeve, was taken 

 in coral, Teviatoa reef, Raiatea Island, Society Islands, August 

 21, 1931. 



Diagnostic characters : The present species has long been 

 confused with Pmctada maxuna Jameson, which is also widely 

 distributed in the Indo-Pacific. From Linne (1760) to Saville 

 Kent (1893) the two species were confused under the Linnean 

 name margaritifera. Kent restricted this name to the larger, 

 more valuable, golden lip or silver-lip shell, but Pace, also Jame- 

 son, have established that Linne's type and descriptions refer to 

 the "black lip" or "Black-edged Banda" shell. 



The colouration of the true margaritifera is quite variable on 

 the external surface of the valves, the ground colour ranging from 

 pale yellowish brown, green, olivaceous, reddish gray to dark 

 brown or black, distinctively marked with radial rows, consisting 

 of cream or yellowish spots extending from the umbo to the mar- 

 gin. Variation in these spots ranges from their enlargement to 

 fuse forming radiating bands, to complete obsolescence. The inte- 

 rior of the lip is similar in ground colour to the external surface 



