100 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
valve obliquely, generally from in front of middle of ventral to behind 
middle of dorsal margin, and somewhat deeper dorsally. Position of 
greatest thickness of carapace located posteriorly, slightly behind middle. 
Left valve the larger, slightly overlapping right along ventral margin 
and the two extremities. Hinge somewhat thickened, occupying approxi- 
mately central third of dorsal margin. In profile acute-ovate, with 
transverse sulcus showing in median region, and with posterior extremity 
slightly inflated. In end view oval and tumid. Surface of valves entirely 
covered with minute, irregularly-arranged, rather inconspicuous 
tubercles, and shell pierced at intervals with minute punctations — 
normal pore canals. Four sub central muscle scars conspicuous, set in 
deepest part of transverse sulcus, generally closer to dorsal margin of 
shell, arranged in row sloping dorsally and posteriorly, and often 
contiguous or nearly so. Two central muscle scars larger and more 
elongate than lateral scars. Shell thin, fragile, chitino-calcareous, and 
transparent to translucent. 
Dimensions of holotype: Length, 0.52 mm.; height, 0.27 mm.; 
approximate thickness of carapace, 0.3 mm. 
Rema/rks: Cypris Miimduranensis does not closely resemble any of 
the described fossil forms of the well-known freshwater genus Cypris 
which today is so abundant in many stagnant pools. The carapace, 
however, is rather similar in structure to that of a recent, but as yet 
undescribed, freshwater species that has been collected from ponds and 
lagoons in S.E. Queensland. It also shows some general resemblance to 
the common species, Cypris gibba Ramdohr, which ranges from Oligocene 
to Recent. 
This is the most abundant species in The Narrows bore-core samples 
examined and, owing to its small size, a large number of undamaged 
valves and some complete carapaces were available for detailed study. 
In fact, the ostracod fauna in some of the samples from The Narrows 
is almost restricted to innumerable individuals of this species, and it has 
also been found to be common in the Petrie Series material examined. 
The specific description, accordingly, is based on a large number of 
specimens. The outstanding characteristics are the obliquely-sloping 
transverse sulcus containing the four muscle scars, the small size, and 
the rather inconspicuous tuberculate and finely punctate ornament — the 
tubercles under high magnification being seen as small, round, somewhat 
flattened prominences surrounded by shallow grooves, and each 
approximately 0.02 mm. in diameter. The variation within the species 
is not great, the most noticeable feature being in the relative position 
of the shallow transverse sulcus on the valves. While in most individuals 
this crosses the valves almost medianly, in some it is located closer to the 
anterior extremity, and in others closer to the posterior extremity of 
the valve. In such cases the position of the muscle scars on the valve 
also varies accordingly. However, after making allowances for apparent 
variations due to different degrees of crushing, the shape of all mature 
individuals of this species has been found to be nearly constant. Also, 
while some very minute and immature forms occur, the size of most 
individuals approximates to the dimensions given above for the holotype 
of the species. In some individuals the shell is thin and horny, but in 
others it is quite calcareous and much more solid. The species has been 
named after the important locality name of Munduran within The 
Narrows Tertiary Basin, where it was first found. 
