168 



Psammobia aequalis, Tate. Plate xvi., fig. 10. 



Reference — Southern Science Record, January, 1885, p. 4. 



Shell compressed ; umbo central, depressed ; transversely 

 elliptic ; attenuated anteriorly ; roundly truncated posteriorly ; 

 sculptured with concentric closely arranged raised lines. 



Dimensions. — Antero-posterior diameter, 22 ; uinbo-ventral 

 diameter, 11 millimetres. 



Localities. — Upper beds at Muddy Creek ; Middle Murravian 

 series near Morgan, on the Eiver Murray (B. T.) ; Table Cape 

 (P. M. Johnston!). 



This species differs from P. Hamiltonensis by the absence of 

 a posterior keel. Its representative in living creation is the 

 British P. tellinella, Lk., from which it differs by its central 

 and depressed umbo, compressed valves, more attenuated 

 anterior margin, and rounded posterior margin. 



Donax Dixoni, spec. nov. Plate xvi., fig. 15. 



Triangularly ovate, subequilateral, the posterior side being a 

 little longer, flatly convex ; posterior margin obliquely trun- 

 cated, anterior side acuminately rounded. Umbones a little 

 oblique, small, situated a little in front of the centre. 



Surface ornamented by broad flatly rounded radial ribs, 

 which are wrinkled by concentric striae and grooves ; on the 

 posterior slope the costa? are not much wider than the inter- 

 vening sulci ; but on the post-medial area the sulci are linear ; 

 the radial costas become obsolete e*i the anterior side. 



Ventral margin of the valves coarsely crenulated. 



Dimensions. — Antero-posterior diameter, 10; umbo-ventral 

 diameter, 6*5 ; sectional diameter of one valve, at about the 

 middle, 2 millimetres. 



Locality. — Lower beds at Muddy Creek. 



Species-name in compliment to Mr. Samuel Dixon, my com- 

 panion on many geological excursions. 



The species has much resemblance to D. cardioides, Lamarck, 

 but is not abruptly inflated medially. 



Donax depressa, spec. nov. Plate xvi., fig. 11. 



Broadly triangularly ovate, very inequilateral, rather de- 

 pressed, but abruptly and sharply elevated from the umbo to 

 the post-ventral angle ; posterior side depressed and roundly 

 truncated at the extremity ; anterior extremity sub-acuminately 

 rounded. The veutral margin is nearly straight, but is incon- 

 spicuously incurved in front of the keel. 



The surface of the anterior portion is almost smooth, finely 

 radially and distantly concentrically grooved ; granulately 

 wrinkled on the keel ; radially and concentrically finely ridged 

 on the depressed, flat posterior area. 



