162 ß(i 



Long. 74 nun., alt. 54 mm. 

 — 59 mm., — 64 mm. 



Distribution:— China Sea, Nagasalu, Yaeyania {'?). 



A few of the specimens collected were attached to Mangrove-roots. Futnre 

 comparative investigations will doubtless prove that 0. riviilnris, Gould (Lischke), 

 is only a form of a previously known species,' but I have thought it right to 

 stop my researches at riimlaris (with which the specimens from Siam entirely 

 correspond), as a large quantity of material is required to arrive at a reliable con- 

 clusion. The whole group (with thin, not folded shell-margin), which includes 

 0. mijfiloides, Lam., nigromarginata, Sow., tiiberciilata, Lam. (= tiibercularis, Reeve), 

 Panhicciae, Crosse (= palmipes, Sow.), the collective species arborea, Ch. and para- 

 sitica, Gm. (which constantly reappear), and many more, must, on account of their 

 great variability, and the hitherto very uncritical and superficial treatment to which 

 they have been subjected, be carefully investigated and may, no doubt, be con- 

 siderably reduced. 



Ostrea Paulucciae, Crosse. 



Ostiea Paiilncciæ, Cisosse, Journ.de Conchyl., vol.17, 1869, p. 188; vol.18, 1870, p. 108, pi. 2, fig. 5. 

 Ostrœa palmipes, Sowerbv, Rekve, Conchol. icon., vol. 18, 1871, Ustriea, Sp. 56. 



S. of Koh Tulu, 10 fathoms, sand mixed with mud (-/s). Sound of Koh Chang, 

 5 fathoms, soft clay (1). S. of Koh Kahdat, 8—10 fathoms, mud (many young odd 

 valves). Between Koh Kahdat and Koh Kut, 6 fathoms, sand mixed with mud (^h). 

 W. of Koh Kut, 15 fathoms, mud (^/a). 



Long. 28 mm., alt. 20 mm. 



Distribution: — Annam, China, Philippines. 



At Koh Chang (in 5 fathoms, on a soft muddy bottom) a smaller specimen 

 was obtained (long. 15 mm., alt. 18 mm.) which seems to me to agree in all points 

 with 0. pes-tigris, Hanl.;^ it is doubtful whether this form also is entitled to rank 

 as a species. 



The specimens from the Gulf of Siam do not correspond exactly with Crosse's 

 description as regards colour, as in almost all cases they are white with a few 

 lilac rays or shades. 



Note. In Morch's Catalogus conchyl. quæ rcliq. comes de Yoldi, II, p. 62, 

 No. 783, there is recorded an Ostrea siamensis, Yoldi, from "Singapuhra," as it is, 

 however, not described, either there or anywhere else, I cannot state anything 

 regarding that form. 



' Dunker (Index moll. mar. Japon., p. 250) refers it to 0. arboiea, Ch. 



- Proc. Zool. Soc. London, Xlll, 1845, p. 107. Taken bj' Cuming at Luzon, Philippines. Reeve, 

 Conchol. icon., XVllI, Sp. 78. Sowkhby (Append, to marine shells of South Africa, 1897, p. 28) is of 

 opinion that 0. pes-ligris (Heeve, fig. 78) is synonymous willi O htcciala, Hani. (= O.laccrans, Ueeve). 



