Ostrea.~\ PELEC'YPODA. 891 



Interior olive in the centre, whitish round the margins, porcellanous. 

 Margin of lower valve eremite below ; there are also minute crenella- 

 tions on the dorsal posterior margin. Hinge-line arcuate, usually with 

 a low posterior lamina in the left valve. Resiliiun in a broadly tri- 

 angular pit, spreading narrowly on both sides of the pit. Adductor- 

 scars large, ovate, subcentral. 



Height, 76 mm. ; length, 66 mm. (type). 



Type, from the Pliocene, in the Dominion Museum, Wellington. 



Hob. Bay of Islands ; Hauraki Gulf (H. 8.) : Manukau. 



Fossil in the Miocene and Pliocene. 



Remarks. On Haliotis shells small oysters are sometimes found 

 adhering with the whole surface of the left valve, which is, of course, 

 smooth, but the right valve has the brown radiate rays, the dorsal 

 margins are crenate within, and the adductor-scars correspond also 

 perfectly with those of typical 0. cornnjntn. The right valve is always 

 uore or less convex : the left flat, but little excavated. 



5. Ostrea glomerata, Gould, 1850. Plate 57, rig. 6. 



Ostmi J<,:ii,emta, Gould, P. Bost, S.N.H., iii, 1850, 34<>. T.S. Expl. Exp., 

 xii, 4dl. atlas f. .377 ; M.N.Z.M., 175. O. mnrda.r, Gould : Hutton, 

 C.M.M., 84 ; not of Gould. 



Shell orbicular crescentic, turning to the left or to the right, left 

 valve deeply concave, with a deep umbonal pit, sharp-ribbed, margin 

 dentate or loled. solid. Beaks usually much produced, curved, con- 

 cave on the inner side. Anterior end convex ; posterior end straight 

 or concave. Sculpture : Left valve with about 6 stout sharp bifur- 

 c;iting ribs, the interstices deep and narrow, crossed by distant con- 

 centric laminae ; right valve opercular. compressed, wrinkled with 

 thick concentric laminse, with dentiform foliations near the margin. 

 Epidermis horny, solid, extending on the margins beyond the inner 

 nacreous portion. Colour slaty-black, with a few well-defined white 

 radiations. Interior white, the margins and adductor-scars purple, 

 upper valve usually blotched with purple. Margins deeply dentated 

 and lobed ; the upper valve is furnished with a few irregularly disposed 

 granules near the hinge, with corresponding pits in the lower valve. 

 Hinge area broad, furrowed. Resilium high and broad. Adductor-scar 

 circular, excavated above, posterior and a little below the middle of 

 the dorso-ventral line. 



Dorso-ventral diameter, about 80 mm. 



Type in the U.S. Nat. Museum, Washington. 



Hob. Northern part of the North Island ; Hauraki Gulf ; Bay of 

 Islands, &c. 



Remarks. This is the highly esteemed Auckland rock-oyster, picked 

 from May to end of September, and consumed in large quantities. 

 Sometimes it is found attached to kelp-roots. 



