OSTKACODS FROM SOME QUEENSLAND TERTIARY BASINS. 105 
conspicuous, five centrally to subcentrally placed forming a rosette, and 
two slightly removed anteriorly and ventrally, arranged obliquely, one 
above the other, sloping ventrally. Rosette consisting of three, generally 
sub-oval, scars in transverse row, with row of two, generally sub-oval, 
scars slightly below. Muscle scars sometimes very close together, and 
some almost or completely coalescent. Two scars above rosette generally 
more elongate and narrower than others. Small accessory muscle scars 
sometimes present, in addition to fundamental seven. Shell of medium 
thickness, chitino-calcareous, generally whitish, and translucent to 
opaque. 
Dimensions of figured specimen from The Narrows: Length, 
1*03 mm. ; height, 0*51 mm. ; approximate thickness of carapace, 045 mm. 
Remarks : In describing this species from the Redbank Plains Series 
in 1935, Chapman had at his disposal only one small sample of ostracod- 
bearing shale, obtained from a surface outcrop. In this rather weathered 
material he found the carapace valves of this species strongly calcified, 
and owing to their opacity he was apparently unable to see the muscle 
scars on the inside of the valves. Recent examination of additional 
samples from Redbank Plains, however, has resulted in the discovery of 
a number of these valves with translucent shells clearly showing the 
muscle scar pattern described above. The species, accordingly, has been 
found to be identical with that recognised in The Narrows material and, 
with the additional material available, a more complete description is 
given. 
E. aequalis compares very closely in shape with E. strigata (Muller), 
but differs from this recent European species, in having the extremities 
rather more broadly rounded, the carapace, particularly the anterior 
portion, more compressed, and in being approximately only half the size. 
No reference is made to muscle scars in the description of this recent 
species. As Chapman (1935, p. 68) has remarked, E. aequalis also 
4 ‘nearly resembles E. glacialis Sars, of the European lakes and marshes, 
in its convex dorsum and evenly rounded extremities.” However, the 
valves, which are somewhat narrower and more compressed than those 
of E. glacialis, are highest slightly in front of the middle. E. aequalis is 
not as narrow or as elongate, although it has the same grouping of 
seven muscle scars, as Candonocypris assimilis Sars, an (H)erpetocyprid 
recorded and figured by Chapman (1919, p. 28) from the Pleistocene of 
Boneo Swamp, west of Cape Schanck, Victoria. The anterior extremity, 
moreover, is more broadly rounded than that of C. assimilis, and there 
are also other differences that separate it from this form. 
This species has been found to be common in some of The Narrows 
bore-core samples, and in all the ostracod-bearing shale examined from 
the Petrie Series and the Baffle Creek Tertiaries. Although very few 
complete, undamaged valves have been found, a large number of valves 
with shells broken to varying degrees have been available for microscopic 
study. The outstanding characteristics of this simple, smooth-shelled 
ostracod are the outline, equality and compressed nature of the valves, 
and the muscle scar pattern. There appears to be little variation in 
shape (apart from the effects of crushing), but variation in the number 
and arrangement of the muscle scars has been noted. In many 
individuals the two scars closest to the dorsal margin have been found to 
be almost coalescent and, in some cases, completely fused into one long 
scar. The addition of a very small muscle scar to the ventral end of 
