Ostrea.] PELECYPODA. 889 



Hab. North and South Islands of New Zealand, but more common 

 in the south, where, in Foveaux Strait and near Stewart Island, 

 extensive beds occur. Also Tasmania and Australia. 



Remarks. This is the southern analogue of the European 

 0. edulis, L., under which name it has been more frequently quoted 

 by conchologicul writers. The beds near Stewart Island are regularly 

 exploited from February to September, and they are in an average 

 depth of 15 fathoms. 



Vernacular Name. Mud-oyster : commonly known as Stewart 

 Island oyster. 



Maori. Tio (fide Captain Bollons). 



Fossil in the Miocene and Pliocene ; Pleistocene in Australia. 



2. Ostrea hyotis, Linne, 1758. Plate 57, fig. 2. 



Mytilits hi/otis, L., Syst. Nat., ed. 10. 1758, 704. Osfmi hi/oti*. L : Hanley, 

 Cat. Rec. Biv. Shells, 308 ; Conch. Icon., xviii, pi. 4, f . 7 ; Tate, T.R.S. 

 S.Aust,, viii, 96, pi. 6, f. 5 ; C. Tert. M.B.M., 299. 



Shell moderately large, of variable, irregular form, suborbicular. 

 triangular to subquadrate, fairly solid, with numerous foliaceous scales, 

 slightly attached by the left valve. Beaks much produced, broadly and 

 flatly convex. Anterior end generally convex ; posterior end straight 

 or lightly convex, frequently with winged processes. Sculpture : Left 

 valve with rrther distant concentric lamellae and numerous angular 

 radiating folds with subtubular patulous spines, which very frequently 

 are only semitubular or reduced to broad foliaceous scales ; right 

 valve flattish, concentrically lamellate, the radiate folds more or less 

 obsolete. Epidermis thick, horny, rather brittle. Colour : Lower 

 valve white, upper valve light to dark brown. Interior light greenish- 

 yellow, white at the margins and near the umbones. Margins sharp, 

 in young specimens the epidermis extending far beyond them. Hinge- 

 line narrow. Cardinal area above high, triangular, somewhat concave. 

 Resilifer triangular. Adductor-scar large, semicircular, subcentral, and 

 slightly posterior. 



Diameter Ant. -post., 75 mm. ; dorso-ventral. 90 mm. : thickm-ss. 

 16 mm. 



Hab. Queen Charlotte Sound, in 16 fathoms (Captain Bollons). 



Remarks. This species is, in Queen Charlotte Sound, almost with- 

 out exception attached by the umbo of the left valve to a Turritella 

 rosea. The type is from the Indian seas. 



Fossil in the Pliocene of Wanganui ; it also occurs in the Eocene 

 of South Australia and Victoria, the older Tertiary of Java, and in 

 the Tertiary of India (as 0. tttbifera, Sow.). 



3. Ostrea Tatei, n.n. Plate 57, fig. 4. 



Ostrea hippopus, Tate, T.R.S. S.Aust., viii, 1886, 98, pi. 4, f. 1 ; not of 

 Lamarck, 1819. 



Shell suborbicular, inequivalve ; hinge-line straight, umbo de- 

 pressed, subcentral ; lower valve with the lower half more or less 



