MIOCENE BYTHOCYPRIDID OSTRACODS 
107 
has resulted in left and right valves with mar¬ 
kedly different length/height ratios. 
Of the bythocypridid species in the late Ter¬ 
tiary of the Port Phillip and Western Port 
Basins. Bythocypris (Bythocypris) subrectangu- 
lata is mainly a shallow water species, although 
it is rare in near-shore facies. B. (Bythocypris) cf. 
affinis , B. (Bythocypris) sp. A and B. (Bytho¬ 
cypris) sp. B occur mainly in deeper water facies 
(Warne 1987). 
Bythocypris (Bythocypris) subrectangulata 
sp. nov. 
Figs I A, 2A-B 
Bythocypris sp.—Whatley & Downing 1983: 352, 
pi. 1, fig. 9. 
Bythocypris sp. 1.—Warne 1987: 441. 
Etymology. A reference to the subrectangular lateral 
outline of the carapace. 
Holotype. Adult LV, female, NM V P122202, from 1 m 
above the base of the Fyansford Formation (Early 
Miocene, late Batesfordian) in the south-west face of 
Batesford Limestone Quarry, near Fyansford, Victoria 
(below the upper limit of Lepidocyclina)\ 38°06'S, 
144°17'E. 
Paratype. Adult RV, male, NMV PI22203. 
Additional material. Fifty-five mainly disarticulated 
valves from the Fyansford and Sherwood Form¬ 
ations. 
Dimensions. Holotype, LV, female, NMV PI22202: 
L = 1.11 mm, H = 0.59 mm. Paratype, RV, male, 
NMV P122203: L = 1.09 mm, H = 0.45 mm. 
Diagnosis. Carapace moderately large, narrow 
and subrectangular, of medium shell thick¬ 
ness. 
Description. Carapace smooth, moderately 
robust for family, narrow in dorsal view but 
without differential compression along marginal 
regions of lateral surface. Margins of both valves 
gently rounded and convex, except ventral mar¬ 
gins which are concave. Maximum length well 
below mid- height; maximum height at mid¬ 
length; maximum width at mid- length and 
slightly below mid-height. Posterior slightly 
more produced and narrower than anterior in 
RV, less so in LV. Normal pore canals simple, 
scattered and without rims. Inner lamellae mod¬ 
erately wide; vestibula larger in anterior than 
posterior; marginal pore canals numerous and 
straight. Hinge long, simple and adont. Adduc¬ 
tor muscle scar pattern consisting of three gen¬ 
erally undivided, elongate anterior scars plus 
one posteroventral scar; middle one of the three 
anterior scars sometimes sutured. Mandibular 
muscle scar pattern consisting of two very 
narrow scars. Frontal muscle scar pattern con¬ 
sisting of one scar above and slightly anterior to 
mandibular muscle scar pattern. Various dorsal 
muscle scars also visible. Sexual dimorphism 
pronounced, males being more elongate than 
females. 
Remarks. This species is similar in lateral out¬ 
line to Bythocypris (Bythocypris?) bradyi (Scott, 
1905). Although Maddocks (1969) recorded a 
range of sizes for B. (B?) bradyi, B. (B.) subrect¬ 
angulata is distinctly larger and not as flattened 
or produced in the anterior region. In addition, 
B. (B?) bradyi has slightly broader inner lamel¬ 
lae, a more symmetrically rounded posterior 
margin, a higher position of maximum length, 
and a thinner shell. B. (B.) reniformis Brady, 
1880 is not as elongated as B. (B.) subrectangu¬ 
lata and has more acutely rounded anterior and 
posterior margins. The new species is assigned to 
Bythocypris s.s. on the basis of its subrectangular 
lateral outline and lack of differential compres¬ 
sion adjacent to the anteroventral and poster¬ 
oventral margins. 
Age andstratigraphical range. Late Early to early 
Middle Miocene (Batesfordian to early Bairns- 
dalian, foraminiferal zones N8-N10/11), in 
clays and marls of the Fyansford and Sherwood 
Formations, as well as in calcilutites of the 
Sherwood Formation. 
Bythocypris (Bythocypris) cf. affinis 
(Brady, 1886) 
Figs IB, 2C-D 
Bythocypris sp. 3.—Warne 1987: 441. 
Anchistrocheles sp. 1.—Warne 1987: 441. 
Material. Eight disarticulated adult and juvenile 
valves from the Fyansford and Sherwood Form¬ 
ations. 
Dimensions. LV, female, NMV PI22204: L = 1.09 
mm, H = 0.55 mm. RV, male, NMV PI22205: L = 
1.07 mm, H = 0.47 mm. 
Description. Carapace elongate, of medium size 
and thickness for family; LV larger than RV. 
Overlap greatest in mid-ventral and antero- 
dorsal regions. Anterior margins of both valves 
symmetrically rounded, with extremities at mid¬ 
height; posterior margins more acutely and 
asymmetrically rounded, with extremities well 
below mid-height. Dorsal margins of both valves 
gently arched, becoming straight anterodorsally; 
