229 



tinguished by tlie great thickness of the test, the convexity of 

 the valve and the crenulation of the pallial line — characters 

 sufficiently striking to warrant specific appellation. The 

 outline of the fossil shell falls within the limits of variation 

 exhibited by the living species, and the external ornamentation 

 is same. 



COEBTJLA EPHAMILLA. 



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

 rounded anteriorly, beaked posteriorly. Eight valve with 

 more than 20 very thick, rounded prominent concentric ridges, 

 the whole surface striated concentrically. The ventral margin 

 is outward-curved medially, and the ridges have a correspond- 

 ing 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. Eight valve 

 with an anterior pointed tooth ; left valve with a stout posterior 

 tooth, flattened and sulcated on its upper surface. Pallial 

 sinus indistinct. 



Length, 2\; breadth, 16; thickness th.Ton^ both valves, 10 

 millimetres. 



Localities. — Table Cape. E. M. Johnston. Abundant in 

 the calciferous sand-rock of the Eiver Murray Cliffs, near 

 Morgan, and in the cotemporaneous deposits at Muddv Creek. 

 (E.T.) 



From the living 0. sulcata, Lamarck, to which it has been 

 referred, our fossil species differs in being less inequilateral, 

 more pointed posteriorly, less gibbous, etc. A nearer ally 

 among existing species is C. fortisidcata, E. Smith, from which 

 it differs particularly in its truncated posterior margin. 



LrCINA PLANA TELLA. 



Left valve orbicular-ovate, equivalve, moderately thin, 

 nearly flat. Surface ornamented with regularly disposed, con- 

 centric, erect, lamelliform ridges of growth, crossed by 

 equidistant radial threads, producing on the dorsal-half an 

 open reticulated appearance ; towards the front the concentric 

 ridges are coarser and the descending strisB finer and nearly 

 obsolete. Umbo depressed, acute ; interior margin smooth. 



Length, 33 ; breadth, 31 millimetres. 



The fossil has no close ally among living congeners. 



