MIOCENE BYTHOCYPRIDID OSTRACODS 
109 
ventral margins gently concave. Maximum 
length below mid- height, maximum height at 
mid-length, and maximum width below mid¬ 
height and approximately at mid-length. Valves 
slightly narrower anteriorly than posteriorly in 
dorsal view. Normal pore canals simple, scat¬ 
tered and without rims. Inner lamellae wide 
anteriorly and narrow posteriorly, both with ves- 
tibula developed. Marginal pore canals (as seen 
in anterior part of carapace) scattered and 
straight. Hinge long, simple and adont. Adduc¬ 
tor muscle scar pattern consisting of three gen¬ 
erally undivided, irregularly rounded anterior 
scars plus one similarly shaped posteroventral 
scar. Mandibular muscle scar pattern consisting 
of two elongate scars. Frontal muscle scar pat¬ 
tern consisting of two semi-detached oval scars. 
Dorsal scars visible. Sexual dimorphism evi¬ 
dent. males being more elongate than females. 
Remarks. This species is similar in size, shape 
and muscle scar arrangement to various subspe¬ 
cies and variants of Bythocypris affinis illus¬ 
trated by Maddocks (1969), but they all have less 
acutely rounded posterior margins. Bythocypris 
(Bythocypris?) sp. (Whatley & Downing, 1983) 
[= Anchistrochdes sp. Whatley & Downing, 
1983] and B. (B?) antemacella Maddocks. 1969 
are also similar but are smaller, thinner shelled, 
more asymmetrically and less acutely rounded 
posteriorly, and slightly more flattened and pro¬ 
duced anteriorly. The possibility that the form 
illustrated here is an intraspecific variant of B. 
(B?) sp. (Whatley & Downing, 1983) is not 
excluded. Previously (Warne 1987), I assigned 
specimens of the present form to two different 
genera on account of the unusually pronounced 
sexual dimorphism. 
Age and stratigraphical range. Early Middle 
Miocene (Balcombian to early Bairnsdalian, 
foraminiferal zones N8/9-N10/11), in clays and 
marls of the Fyansford and Sherwood Forma¬ 
tions. 
Bythocypris (Bythocypris) sp. A 
Figs 1C, 2G-H 
Bythocypris sp. 2.—Warne 1987: 441. 
Material. Thirty-six disarticulated adult(?) and juve¬ 
nile valves from the Fyansford and Sherwood Forma¬ 
tions. 
Dimensions. LV, female?, NMV PI22206: L = 0.79 
mm, H = 0.44 mm. RV. male?, NMV PI22207: L = 
0.80 mm, H = 0.35 mm. 
Remarks. This form is very similar to Bythocy¬ 
pris (Bythocypris) subrectangulata in the shape 
and clustering of the muscle scars but is smaller, 
more acutely rounded posteriorly, and has a 
higher posterior extremity and a greater height 
to length ratio. The differences in shape are 
approximately the same if B. (B.) sp. A. is com¬ 
pared with similar sized juvenile specimens of B. 
(B.) subrectangulata. Furthermore, the inner 
lamellae in juveniles of B. (B). subrectangulata 
are narrower and are usually uncalcified. B. (B.) 
sp. A is most abundant in deeper water units of 
the Fyansford Formation at Mornington, where¬ 
as autochthonous occurrences of B. (B.) subrect¬ 
angulata are restricted to the shallow water units 
of the Fyansford Formation at the Batesford 
Limestone Quarry (Warne 1987). 
Maddocks (1969) noted that some bairdi- 
acean species have the capacity to develop calci¬ 
fied inner lamellae in juvenile stages. It is poss¬ 
ible, therefore, that the differences in carapace 
features between Bythocypris (Bythocypris) sub¬ 
rectangulata and B. (B.) sp. A merely reflect eco- 
phenotypic variation within a single species. 
Age and stratigraphical range. Early Middle 
Miocene (Balcombian to early Bairnsdalian, 
foraminiferal zones N8/9-N10/11), in clays and 
marls of the Fyansford and Sherwood Forma¬ 
tions. 
Bythocypris (Bythocypris) sp. B 
Figs ID, 21 
Bythocypris sp. 4.—Warne 1987: 441. 
Material. One LV from the Fyansford Formation. 
Dimensions. LV, NMV PI22208: L = 0.87 mm, H = 
0.41 mm. 
Remarks. This specimen is similar in shape and 
height/length ratio to Bythocypris (Bythocypris) 
prolata Maddocks, 1969 but is smaller than 
adults of that species. 
Age and stratigraphical range. Early Middle 
Miocene (Balcombian, foraminiferal zones 
N8/9), in clays of the Fyansford Formation. 
Subgenus Bythocypris (Bythotriangularia) 
subgen. nov. 
Etymology. A reference to the family Bythocyprididae 
and to the subtriangular carapace. 
Tvpe species. Bythocypris spiriscutica Maddocks, 
1969: 96-99, figs 49E-I, 50A-D, 51A-E. 
Other species. B. (Bythotriangularia) eltanina (Mad¬ 
docks, 1969); B. (Bythotriangularia) mozambiquensis 
