112 16 



Area (Barbatia) decnssata, Sowebby, Martini u. Chemnitz, Conchyl. Cabin, VIII, 2 Abtli.. ]). 144, pi. 37, 



figs. 2—5. 

 — — — — E. Lamy, Bull, du Mus. d'Hist. Nat. Paris, 1904, p. 273. — Lw. cit. 



1906, p. 317, No. 78. 

 Byssoarca uelata, Sowerby, Proc. Zool. Soc. London, vol. I, 1833, p. 18. 

 Area — — Reeve, Conchol. icon., II, Area, Sp. 79. 



Barbatia — — var., Dunkek, Novitates conchologicae, p. 124, pi. 41. 



Area (Barbatia) velata, Sowebby, Martini u. Chemnitz, Conchyl. Cabin., VIII, 2 Abth., p. 207, pi. 49, 



figs. 2 -3. 



The north side of Koh Mesan, 10 — 15 fathoms, stones (1). Koh Chick, rocky 

 coast (3). North end of Koh Chang, 1 fathom, old coral blocks (38). The same 

 locality, 12 fathoms, old coral blocks (4). West coast of Koh Chang, 10 fathoms, 

 mud (5). Koh Sarlak (2). Lem Ngob, on piles of bridge, very low tide (2). Koh 

 Lom (3). Strand of Koh Kahdat (1). Koh Mak, sand coast (1 + •'/.,) 



"Sinum Siamensem habitare dicitur" (Barbatia uelata, Sow. var.. Dunker). Islands 

 in the Gulf of Siam (A. complanata Ch., L. Morlet, loc. cit.). 



Long. 8—55 mm. 



Distribution:— Singapore,' Salanga, Mergui Archipel, Nicobar Isis., Madras, 

 Ceylon, Persian Gulf, Gulf of Aden, Red Sea, Gulf of Suez and Akaba, Seychelles, 

 Madagascar, Mascarenes. — Poulo Condor, China, Japan, Philippines, Celebes, Torres 

 Strait, New Caledonia, Viti Isis., Funafuti (EUice Isl.), Paumotu Isl., Society Isis., 

 New Zealand, Galapagos Isis. (San Thome in the Gulf of Guinea, Hoyle?). 



On the basis of the material at hand, I have united Area decussata, Sow. 

 with A. velata, Sow. into one species, as it is not possible to keep these forms 

 distinct, A. decussata merging by easy stages into A. velata, while the specific charac- 

 ters which have been pointed out, are not constant. In PI. 1, Figs. 5—10 I have 

 figured several forms which show this transition better than it could be shown by 

 any description. It was undoubtedly owing only to the lack of a larger quantity 

 of material that Sowerby established two species upon specimens taken in the 

 same localities ("Lord Hood's and Chain Islands, Pacific Ocean, attached to shells. 

 Cuming")."^ The literature gives indications of the great uncertainty which authors 

 show in the determination of the highly variable ß«rZ>a/ia-forms; while a great 

 number of species: — A. foliata, Forskå], '• revelata, Dsh., Petersi, Dkr. , sculptilis. Reeve 

 and many others need to be known in more complete development- and varia- 

 tion-series before their distinctness can be guaranteed. The reported occurrences of 

 the West-Indian species Area Heblingi, Ch. (cundida, Gmel.) in Asiatic waters are 

 without doubt due to erroneous determinations, and all the specimens in question 

 should evidently be referred to A. complanata; nor is A. nivea, Ch. sufficiently defined 

 as a species, and it needs revision.* Pagenstecher however, goes loo far,' when 



' Taken by the Danish E.\pedition to Slam, four specimens, in 2 — 3 fathoms, coral-reef. 

 "' In spite of Chemnitz's naming Guinea as the home of his species A. complanata, an undoubtedly 

 incorrect statement, I have not hesitated in referring the forms we are here considering to tliat species. 

 '■' v. Martens, Vorderasiat. Conchylien 1874, p. 103, pi. 9, fig. 58. 



^ Ei>. Lamy, .lonrn, de Conchyl., vol. .'■)2, 19Ü4, p. 140. — Bullet, du Mus. d'Hist. Natur., 1904, p. 272. 

 '"' Ueber die von B, Kossmann am Botheu Meere gesainm. Mollusken, Lpzg. 1877, p, 35. 



