169 



Margin of the valves plain. 



Dimensions. — Antero-posterior diameter, 37 ; umbo-ventral 

 ^diameter, 25 ; sectional diameter of one valve, 6 millimetres. 

 Locality. — Oyster beds at Nor.'- West Bend, Biver Murray. 



FAMILY SEMELID.E. 

 Semele vesiculosa, spec. nov. Plate xvi., fig. 12. 



Transversely ovate, inequilateral, somewhat inflated. The 

 interior side is the longer and rounded, the posterior side is 

 obtuse angled; slightly inequivalve, the right valve not so con- 

 vex as the other, and less inconspicuously angled at the um- 

 bonal slope ; umbones acute, approximate, situated a little 

 behind the centre ; front dorsal margin slightly incurved 

 in front of the beaks ; post-dorsal margin slightly arched, 

 with a considerable descending slope ; ventral margin 

 broadly arched at the front and middle, slightly insinuated 

 posteriorly. Lunule broadly lanceolate, hardly impressed. 



Exterior surface, glossy, white, with a few growth lines. 



Left valve with one cardinal tooth in front of and rather 

 distant from the short narrow oblique cartilage pit, sometimes 

 with a small short lamina arising from the distal end of: the 

 cardinal tooth and directed backwards. Right valve with two 

 divergent cardinal teeth in front of the cartilage pit. There 

 is a well-developed lateral on each side. The pallial sinus is 

 wide, broadly rounded at the apex, and extending for two- 

 thirds across the interior. 



Dimensions. — Antero-posterior diameter, 9 ; umbo-ventral 

 diameter, 6 ; sectional diameter of both valves, 5 millimetres. 



Locality. — Not rare in the lower beds at Muddy Creek. 



Vail, with longer posterior side and more pointed extremity 

 common in the calciferous sandstones of the River Murray 

 Cliffs near Morgan. 



Semele Krauseana, spec. nov. Plate xvi., figs. 18a — 18&. 

 Transversely-oval, inequilateral, thin, moderately convex ; 

 the valves a little unequal, both are turned conspicuously to 

 the right at the hinder end, and there slightly gaping. The 

 anterior side is the longer and rounded, the posterior subros- 

 trated, with a slight fold continued from the umbo to the post- 

 ventral margin. The umbones are very small, acute, contiguous, 

 situated at four-sevenths of the whole length from the front ; 

 lunule lanceolate concave. The dorsal margins are straight, the 

 hinder more rapidly sloping than the front; the ventral margin 

 is broadly arched anteriorly, slightly incurved, aud rapidly as- 

 cending posteriorly. The exterior surface is shining, white, with 

 one or two zones of colour ; concentrically finely striated. 



