9S 



O. corrugata, Hutton, but the single specimen o£ that species 

 which I possess is too imperfect for critical comparison. 



An extreme variety occurs in the Upper Murraviau at the 

 jS^orth-AVest Bend, attached to Meleagrina by whole surface, 

 ■except a narrow erect expansion which is externally laminated 

 and occasionally plicatedly wrinkled ; the upper valve is 

 .smooth and has the pointed recurved umbo so characteristic of 

 the Aldinga specimens. 



A thin-shelled form, having much resemblance to the last 

 variety, which was obtained from the Adelaide bore may for 

 the present be associated therewith. 



Localities. — Upper Aldinga series at Aldinga and Adelaide. 



A^ar. a. — Upper Murraviau, North- AVest Bend, on the Elver 

 Alurray. 



A"ar. 1). — Lower Aldinga series at Adelaide. A minute valve 

 having a thick test showing irregular structure from Schuapper 

 Point, Hobson's Bay. 



Ostreahippopus, spec, nov. Plate iv., figs, la — 16. 



Shell suborbicular, inequivalve ; hinge-line straight, umbo 

 depressed, sub-central. Upper valve nearly flat, undulose to- 

 wards the margin, w^hich is included within the lower valve ; 

 surface with irregularly concentric lamellae. Lower valve 

 attached by a very large surface with an erect margin, which 

 is externally faintly wrinkled and striate longitudinally, and 

 lamellose concentrically. 



Dimensions. — Length, G6 ; height, 60 ; depth of elevated 

 front, 40 millimetres. 



Locality. — Glauconitic limestone, Aldinga Bay. 



Subgenus G-etpiijea. 

 Gryphsea tarda, Hutton. Plate vi., figs. 2rt — 2&. 



Hef. — Hutton in Cat. Tert. Poss. of Xew Zealand, p. 35, 

 1873. 



Shell rather thin, oblong or irregularly rotund. 



Inferior valve tumid very convex, smooth, with broadish folds 

 of growth ; free or sessile by a small umbonal area ; anterior- 

 ventral margin produced into a conspicuous lobe ; umbo sub- 

 acute, incurved and bent forward ; ligamental area broad, 

 moderately excavated medially ; muscular impression oblong, 

 situated towards the margin on the produced side. Superior 

 valve flat with an elevated margin, ornamented with imbricating 

 lamell.T. 



Dimensions.— l.\iiQiY\QY valve, height, 45 ; breadth, 32 ; thick- 

 ness, 23 millimetres. 



Jjocalities. — Glauconitic limestones and polyzoal rock, north 

 side of Blanche Point, Aldinga Bay ; chalk rock of the Bunda 



