65 161 
lata, Born (and var. Forskali, Chemn.), were taken in Pliocene Deposits in Egypt 
“in the Lake Deposits of Wadi Natrun at the hill known as Moluk.”! 
Ostrea hyotis L. 
Mytilus Hyotis, Linné, Syst. Nat., ed. 10, 1758, p. 704, No. 207. — ed.12, p.1155, No. 244. — Mus. Ludov. 
Ulr., p. 538, No. 129. 
Ostrea_ hypolis, — Reeve, Conchol. icon., XVIII, 1870, Ostraea, Sp. 7. 
Var. imbricata, Lamarck. 
Ostrea imbricata, Lamarck, Hist. nat. d. anim. s. vert., VI, 1 part. 1819, p. 215, No. 46. — éd. 2, VII, 1836, 
p. 235, No. 46. 
Ostrea -- —_ REEVE, Conchol. icon., XVIII, Ostraa, Sp. 36. 
Koh Kram, 30 fathoms (1/2). S. of Koh Chuen, 30 fathoms, shells (°/2). Coast 
of Lem Ngob (1). S. of Koh Kahdat, 8—10 fathoms, mud (1). E. of Koh Mak, 20 
fathoms, mud (1) (Singapore; Sv. Gap. 1/2). 
Specimen from Koh Kram: long. 74 mm., alt. 46 mm. 
= — Koh Kahdat: long. 33 mm., alt. 49 mm. 
— — Koh Chuen: long. 21 mm.,, alt. 24 mm. 
— — Koh Mak: long. 57 mm., alt. 49 mm. 
Distribution: — O. hyotis has been recorded from: — Ceylon, Gulf of Manaar, 
Gulf of Aden, Seychelles, Amirantes, Mauritius, Zanzibar. — Poulo Condor, China, 
Loo Choo Isls., Japan, Philippines, Moluccas, Viti Isls. 
O. imbricata has been recorded from: — China, Japan, Java, New Guinea, and 
by Metvitt & STaNpDEN from the Persian Gulf and the Mekran coast. 
Since DesHayes (in the second ed. of Lamarck, Anim. s. vert.) wrote regarding 
O. imbricata that “Cette espéce est inutile, elle a été faite avec une variété jaune de 
la suivante (O. hyotis, Ch.); il faudra done les réunir sous la dénomination d’ Ostrea 
hyotis,’ some later authors have upheld the specific distinctness of both the species 
(DuNKER, REEVE, PitsBry), some regard them either as varieties or as the same 
species (KtsTER, HANLEY, Morcn). 
O. inermis, Sow., is no doubt synonymous with O. imbricata, Lam. 
Ostrea rivularis, Gould (Lischke). 
Ostrea rivularis, GouLD, Proceed. Boston Soc. Nat. Hist., vol. VIII, 1861, p. 39. 
= = = LiscHkE, Japanische Meeres Conchyl., I, 1869, p. 176, pl. 14, figs. 2—3. 
Gulf of Rayong, 7—10 fathoms, sand and mud (‘/:). S. of Koh Samit, 20 
fathoms, mud (?/2). Coast of Lem Ngob (1). Sound of Koh Chang, 5 fathoms, soft 
clay (4). E. of Koh Mak, 20 fathoms, mud (‘/:). Between Koh Kut and Koh Kahdat, 
10 fathoms, shells (one specimen, and some young odd valves). Strand of Koh 
Kahdat (?/2) (Singapore, shallow water, one specimen; Sy. Gap). 
1 R. BULLEN NEwron, On some Pliocene and Post-Pliocene Shells from Egypt (The Geological 
Magazine. New Ser., dec. IV, vol. 6, 1899, p. 402, pl. 19, figs. 1—5). 
D. K. D. Vidensk. Selsk. Skr., 7. Reekke, naturvidensk. og mathem. Afd. V. 3. 91 
