160 



Dimensions. — x\ntero -posterior diameter, 27 ; umbo-ventral 

 diameter, 20 ; sectional diameter of both valves, 13 milli- 

 metres, 



Locality. — In the clayey green sands, Adelaide bore. 



Cythera eburnea, spec. nov. Plate xviii., fig. 7. 



Ovate- snbtrigonal, inequilateral, rather thin and convex,, 

 sub-acuminate anteriorly, and bluntly rounded posteriorly. 

 The umbones are rather small, moderately acute, curved over 

 towards the front, situated at about one-third of the whole 

 length from the front. The dorsal margin descends consider- 

 ably on both sides, the anterior nearly straight, the posterior- 

 much longer, and slightly arched ; the ventral outline is -gently 

 curved, ascending much more in front than behind. Lunule, 

 large, broadly cordate, scarcely sunken, a little elevated along 

 the middle, circumscribed by an impressed line, and striated 

 by growth lines. 



The exterior is smooth, shining, white, marked at intervals 

 with narrow subtranslucent zones, and ornamented with a few 

 incised lines and striae, developing into raised threads at the 

 extremities. 



The pallial sinus is moderately deep, obliquely ascending, 

 and sharply rounded at the end. 



The margin of the valves is plain. 



Dimensions. — Antero-posterior diameter, 16 ; umboventral 

 diameter, 13 ; sectional diameter of both valves, 10 millimetres. 



Localities. — Common in the older beds at Muddy Creek, and 

 in the calciferous sandstone of the Hiver Murray Cliffs near 

 Morgan ; also in the yellow sand rock, Corio Bay ; in the blue- 

 clays at Schnapper Point, Port Phillip ; Table Cape (JR. M. 

 Johnston !) . 



Cytherea submultistriata, spec. nov. Plate xviii., figs. 6 and 8. 



Transversely elongate-ovate, moderately convex, thick ; 

 anterior side shorter ; posterior side subacuminately produced. 

 Surface with distant growth folds and finely concentrically 

 striated. Lunule lanceolate, shallow, defined by an impressed 

 line. The pallial line is much nearer to the margin than in 

 allied species ; the sinus is wide and deep, reaching to the 

 centre of the valve ; it is obliquely narrowly truncated at the 

 end. 



Dimensions. — Antero-posterior diameter, 30 ; umbo-ventral 

 diameter, 22 ; sectional diameter of both valves, 14 milli- 

 metres. 



Localities. — Upper .beds at Muddy Creek ; variety (fig. 6), 

 in a well-sinking, Cooke's Plains, east of Wellington, Eiver 

 Murray. 



