28 
ends large, margins long and obliquely truncated, Umboncs obtuse and 
a])parently llattened from above (not well preserved) ; Hanks of the valves 
much inllated, particularly in tbe umbonal region. Posterior diagonal ridges 
obtuse, but strong ; posterior slopes steep and tlattened. Surface with 
numerous gradate, regular and sharp-edged concentric rugiio, each edge with 
a faint subordinab' line below il, the Avhole becoming less regular toAvards 
the ventral margins ; tlie intersjAaces between the rugm are concaA^e and shoAV 
traces of epidermal filjres. 
Ohs. — I figure this shell in the hope that it may be the means of 
bringing further specimens to light. I cannot assert with any degree of 
certainty that it is a member of the Arcacea, as the space that should, in 
such a case, represent the area is so filled AA'ith irrcmoA'able matrix, and the 
apical portions of the umbones so obliterated, that the presence or absence of 
an area is in doubt. At the same time the obliquely sub-rhomboidal outline 
reminds one of the group in question, but it is certainly distinct from 
any shell, so far described in works accessible to mo, from the Australian 
Cretaceous. 
Loc . — Mount Poole Station, near Milparinka, North-lVest N. S. Wales 
{A. Lang). 
llor. — LoAver Cretaceous ? 
Colin . — Mining and Geological Museum, Sydney. 
CYRENOPSIS/ gen. nov. 
Gen. C4ar.— Shell inflated, subtrigonal to moderately rounded, sub- 
incqiulateral, alAA^ays more or less produeed posteriorly ; margins simple and 
closed. Taa o entire, unequal, posteriorly directed cardinal teeth in the right 
valve, one above the other ; a subcentral entire triangular cardinal and an 
oblique posteriorly directed one above it in the left valve, and two smooth 
laterals. Umhones contiguous, slightly opisthogyrate ; ligament opisthodetic, 
AA’cll developed and A'ariahle in length ; escutcheon long, rather deep, and 
inclined to be straight-walled at the sides; lunule absent. Adductor 
impressions A'arial)le in development; pallial sinuses inconspicuous, even it 
present. Sculpture concentric. 
Cyrena, and opxi-^, signifying resemblance to. 
