176 



species is distinguished by the coarser and more distant 

 liration. 



Myodora aequilateralis, Johnston. Plate xvii., fig. 8. 



Reference. — Proc. Hoy. Soc, Tasmania, for 1879, p. 40. 



Left valve solid, trigonal, equilateral, flat, or slightly con- 

 cave ; dorsal margins equally sloping, inclined to one another 

 at an angle of 90 deg. ; the front-dorsal margin straightish, or 

 slightly arched ; the post-dorsal margin straight, or slightly 

 incurved behind the umbo ; ventral margin roundly arched. 

 Eight valve unknown. 



Surface ornamented with close, fine concentric ridges of 

 growth and striae and microscopic granules, the former forming 

 nodulose denticulations on the front-dorsal edge. 



Dimensions. — Antero-posterior diameter, 25 ; umbo-ventral 

 diameter, 21 millimetres. 



Localities. — Table Cape (B. If. Johnston /) ; Schnapper 

 Point, Hobson Bay (R.T.) ; upper beds at Muddy Creek (J. 

 Dennantl). 



FAMILY CORBULIDJ3. 

 Corbula ephamilla, Tate. Plate xvii., figs. 13a— 13&, and 14. 



Reference. — Proc. Roy. Soc, Tasmania, for 18S4, p. 229. 



Shell solid, very inequivalve, inequilateral, ovately-trian- 

 gular, rounded anteriorly, beaked posteriorly. Eight valve 

 with more than twenty very thick, rounded prominent concen- 

 tric ridges, the whole surface striated concentrically. The 

 ventral margin is outward-curved medially, and the ridges have- 

 a corresponding flexure. The posterior margin is obliquely 

 truncated, carinated from the umbo to the post-ventral margin ; 

 posterior to the carina is a somewhat concave area on which 

 the concentric folds are continued as multiplied lamellae. The- 

 umbo is in the anterior third, flat, incurved, and with small 

 ridges. Left valve ovately triangular, nearly flat, pointed 

 behind, carinated from the umbo to the post-ventral margin ; 

 surface irregularly striated by lines of growth ; umbo flattish, 

 from below which two distinct ridges radiate to the ventral 

 margin, one or two additional but shorter ones sometimes- 

 occur. Young shells distantly radially striated, the striae more 

 prominent and closer on the posterior slope. Eight valve with 

 an anterior pointed tooth ; left valve with a stout posterior 

 tooth, flattened and sulcated on its upper surface. Pallial 

 sinus indistinct. 



Dimensions. — Antero-posterior diameter, 21 ; umbo-ventral 

 diameter, 16 ; sectional diameter of united valves, 10 milli- 

 metres. 



Localities. — Tasmania: Table Cape (R. M. Johnston I). 



