161 



This species resembles the living O. mult 1st Hat a, Sow., 

 C. disrupta, Sow., and C. Diemenensis, Hanley ; in its oval out- 

 line it comes nearest to C. multistriata, but its post-dorsal 

 margin is straight, and the pallial line and sinus are different, 

 being like those in C. disrupta. 



The variety (fig. 6), of which only one specimen has been 

 obtained, makes some approach to C.eburnea; it is shorter and 

 more convex than the type, but is connected with it by two 

 examples from Muddy Creek. 



Gexus Dosinia. 



synopsis of species. 

 Regular concentric ridges. 



Valve flat ; ridges thick, depressed. D. Johnstoni. 



Valve rather tumid ; ridges thin, erect. D. Orayii. 



Inequidistant concentric sulcations. D. imparistriata. 



Dosinia Johnstoni, spec. nov. Plate xiv., figs. 9 and 12. 



Orbicular, lenticular, moderately convex, somewhat thin and 

 glossy, inequilateral. 



Umbones moderate, curved forward, and situated at about 

 one-fourth of the whole length of the valve from the front. 

 Lunule ovately-cordate, short, impressed, elevated in the 

 middle, very finely striated. 



The exterior is ornamented with concentric ridges, which are 

 regular, numerous, thick, depressed, with reflexed acute edges, 

 and separated by linear deep sulci (about 20 in a breadth of 10 

 millimetres, measured from the ventral margin) ; at the ex- 

 tremities the lira? are fewer, and are here and there raised into 

 more or less elevated scales. The posterior hinge area some- 

 what angulated and lamellated. 



The pallial sinus is triangular, with a broad base, extending 

 horizontally to a little beyond the middle of the valve; apex 

 acute. 



Dimensions. — Antero-posterior diameter, 27 ; umbo-ventral, 

 25 ; sectional diameter of one valve, 7 millimetres. 



Localities. — Upper beds at Muddy Creek, Hamilton ; Table 

 Cape (B. M. Jolinston /) 



Dosinia Grayii, Zittel. 



Reference. — Pal. von INeu-Seeland, p. 45, t. 15, f. 11; id, 

 Hutton, Tertiary Moll, of N. Zealand, p. 22, 1873. 



" Orbicular, solid, tumid, sub-a?quilateral, with distant con- 

 centric lamella?, more elevated at the extremities. Umbos 

 inflated, incurved, acute. Anterior side sloping, rounded pos- 

 teriorly ; lunule large, oblong-cordiform, deeply impressed, 



M 



