MIOCENE BYTHOCYPRIDID OSTRACODS 
113 
ventral margins. These specimens may belong to 
Anchistrocheles , a view that is supported by the 
shape and areal extent of the inner lamella 
which, although less extensive than that of A. 
praebensoni, is similar in size to that of A. 
fumata. 
Anchistrocheles praebensoni is restricted to 
shallow water facies of the Port Phillip and 
Western Port Basins. 
Ageandstratigraphical range. Late Early to early 
Middle Miocene (Batesfordian to Balcombian; 
foraminiferal zones N7/8-N8/9), in calcare- 
nites, calcilutites and marls of the Batesford 
Limestone, Fyansford Formation and Sherwood 
Formation. 
Genus Orlovibairdia McKenzie, 1978 
Type species. Bythocypris angulata Brady, 1870. 
Remarks. Orlovibairdia is very similar to Anchis¬ 
trocheles in carapace morphology, and both gen¬ 
era include forms with a reniform lateral outline. 
Orlovibairdia species tend to be more elongate, 
however, and the genus as a whole encompasses 
forms with a broader range in lateral outline, 
from reniform to subrectangular. Orlovibairdia 
also differs from Anchistrocheles in possessing 
less extensive inner lamellae, strong anteroven- 
tral and posteroventral denticulation, and, in 
some species, coarse punctate ornament. 
Some species of Orlovibairdia resemble 
Pussella and Danipussella in lateral outline, but 
members of the last two genera have signifi¬ 
cantly greater length to height ratios. 
Orlovibairdia mooraboolensis sp. nov. 
Figs IF, 2E-F 
Orlovibairdia sp. 1.—Warne 1987: 441. 
Etymology. A reference to the type locality near the 
Moorabool River at Fyansford, Victoria. 
Holotype. Adult LV, female, NM V P12221 1 from near 
the middle of the Fyansford Formation (Middle Mio¬ 
cene, Balcombian) in the south-west face of Batesford 
Limestone Quarry, near Fyansford, Victoria (base of 
middle quarry bench above the upper limit of Lepi- 
docycltna sp., approximately 10 m above the boundary 
with Batesford Limestone); 38°06’S, 144' 17’E. 
Paratype. Adult RV, male, NMV PI22212. 
Additional material. Twenty-five disarticulated adult 
and juvenile valves from the Fyansford and Sherwood 
Formations. 
Dimensions. Holotype, LV, female, NMV PI22211: 
L = 0.67 mm, H = 0.37 mm. Paratype, RV, male, 
NMV P122212: L = 0.66 mm, FI = 0.31 mm. 
Diagnosis. Carapace relatively small, smooth 
and elongate, with conspicuous differential 
compression of anteroventral and posteroven¬ 
tral margins which are strongly denticulate. 
Description. Carapace thin shelled; anteroven¬ 
tral margin with six denticles; posteroventral 
margin with nine denticles. LV larger than RV 
and overlapping it. LV asymmetrically rounded 
anteriorly, with convex anterodorsal and ante¬ 
roventral margins; extremity below mid-height. 
Posteriorly, LV more acutely rounded with con¬ 
vex posterodorsal and posteroventral margins; 
extremity below mid-height. RV similar to LV 
anteriorly and posteriorly but with straight ante¬ 
rodorsal margin. Dorsal margin arched in LV, 
straight in RV. Ventral margins of both valves 
strongly incurved. Maximum length slightly 
below mid-height; maximum height at mid¬ 
length in LV, anterior of mid-length in RV; 
maximum width below mid-height and at mid¬ 
length. Normal pore canals open, scattered, 
some with rims. Inner lamellae relati vely narrow 
compared with type species, wider anteriorly 
and anteroventrallv than posteroventrally. Ves- 
tibulum evident but small. Marginal pore canals 
(as seen anteriorly on carapace) scattered and 
straight. Adductor muscle scar pattern consist¬ 
ing of four subrounded to elongate scars in a 
loose aggregate; individual scars sometimes 
complexly sutured but no discrete division 
observed. Sexual dimorphism pronounced, 
males being more elongate than females. 
Remarks. Orlovibairdia mooraboolensis is simi¬ 
lar to O. angulata but the latter is slightly larger 
and possesses a scattered punctate ornament. O. 
cf. arcaforma (Swanson, 1979) [species attri¬ 
buted to Swanson by McKenzie 1978 but a 
nomen nudum when cited] differs from the new 
species in having a subrectangular lateral outline 
and strong punctate ornament. O. formosana 
Hu, 1981 from the Pliocene to Pleistocene of 
Taiwan is smooth like O. mooraboolensis but has 
a subrectangular lateral outline and a denticu¬ 
late anterodorsal margin. 
The variation in lateral outline and ornament 
outlined above in Orlovibairdia species illus¬ 
trates the mosaic of carapace characters within 
the genus. 
Age and stratigraphical range. Early Middle 
Miocene (Balcombian to early Bairnsdalian; 
foraminiferal zones N8/9-N10/11), in marls 
and clays of the Fyansford and Sherwood For¬ 
mations. 
