173 



The posterior area is coarsely granulated, tlie rest o£ the- 

 surface less so ; conspicuous folds of growth occur at irregular 

 intervals. 



Dimensions. — Antero-posterior diameter, 33 ; umbo-yentral 

 diameter, 21 ; sectional diameter of right valve, 7 millimetres. 



Localities. — Muddy Creek (lower beds) — a right valve only; 

 Adelaide bore, a left valve, probably of the same species. 



Among recent species this fossil shell is much like T. speciosa, 

 Angas, but is less inequilateral, and more attenuated at the front. 



G-enus Mtodoea. 



synopsis of the species. 

 A. Elongate, subinequivalve. 



Anterior side five times as long as the posterior ;- 



broadish. M. prcelonga. 



Anterior not much longer than the posterior ; very 



narrow. M. angustior. 



b. Eight valve convex ; left valve flat. 



Eight valve oblong; finely concentrically ridged, radially 

 striated. M. tenuilirata. 



Eight valve ovately-oblong, with numerous close con- 

 centric ridges. M. australis. 

 Eight valve ovate, with few distant concentric ridges. 



JSI. corrugata. 

 Eight valve triangularly ovate, somewhat acuminate- 

 anteriorly ; left valve truncated posteriorly. 



M. lamellata. 

 ? ? ; left valve equilaterally trigonal. 



M. ceqiiilateralis. 



Myodora prselonga, spec. nov. Plate xix., figs. 12a— 12d. 



Elongately-oblong, thickish, inequivalve, very inequilateral, 

 the anterior side being about five-sixths the total length r 

 anteriorly rounded and posteriorly vertically truncated. The 

 front dorsal slope is slightly convex, the post-dorsal margin 

 incurved behind the umbo, ventral margin almost straight, and 

 horizontal ; the post-dorsal slope is bluntly angulated. 



The surface of the valves is smooth, with concentric growth 

 lines. 



The pallial sinus is broad, rounded at the end, and extends to 

 nearly half the length of the shell. 



The right valve is moderately convex, the other is depressed, 

 almost flat. 



Dimensions. — Antero-posterior diameter, 14; umbo-ventral 

 diameter, 7*5; sectional diameter of right valve, 225 millimetres. 



