J. V. NEIL 
suggest that the specimens do not belong to 
Miracythere. 
Miracythere sp. A 
Figs 1A, C-D, 2A-B, 3A, C-F 
Material. The specimens originally found consisted of 
one adult left valve (Figs 1 A, D, 2A-B. 3A, C-F), one 
juvenile left valve, and fragments of two valves, all of 
which were lost in transit to the laboratory of the Geo¬ 
logical Survey of Victoria. Subsequent repicking of the 
sample produced two broken juvenile valves, one left 
(NMV PI23311, Fig. 1C) and one right (NMV 
PI23312). The catalogue numbers refer to the inver¬ 
tebrate palaeontological collection of the Museum of 
Victoria, Melbourne. 
Horizon and locality. Muddy Creek Formation, Clif¬ 
ton Bank, Muddy Creek near Hamilton, southwestern 
Victoria. 
Age. All the specimens came from the oldest level at 
Clifton Bank (Sample 9), of late Early or early Middle 
Miocene (Batesfordian) age (N8 in the planktonic 
foraminiferal zones of Berggren et al. 1985; the revised 
correlation of magnetic anomalies by Berrgren et al. 
has shifted ages 1.5 to 2.0 my younger in the Middle 
Miocene, so that the position of the Early-Middle 
Miocene boundary' in relation to the Australian 
Bairnsdalian and Balcombian stages is open to 
debate.) 
Dimensions. Adult LV: L = 0.65 mm; H = 0.38 mm; 
W = 0.23 mm (figured specimen, now lost). The re¬ 
picked specimens NMV PI23311 and P 123312 are 
too fragmentary to measure. 
Description. Valve medium-sized in adult; sub¬ 
elliptical in outline, hyaline and thinly calcified. 
Surface smooth. Normal pore canals simple and 
widely scattered. Dorsal margin straight. Ven¬ 
tral margin straight to slightly sinuous, subparal¬ 
lel to dorsal margin except posteriorly. Anterior 
and posterior gently rounded in outline, former 
more so than latter. Anterodorsal and postero- 
dorsal angles broadly and evenly rounded. 
Shallow, vertical median sulcus. Prominent 
hollow tubercle developed anterodorsally (Figs 
1 A, 3A), ornamented with three spines on dorsal 
edge. Valve inflated, with well-developed and 
sharply-defined flattened ventral zone; less 
marked flattening anteriorly and posteriorly. 
Inflation of valve greatest in posterior third. 
Marginal zone of valve and inflated area orna¬ 
mented with flat spatulate spines (Fig. 3E) that 
vary in orientation, from normal to plane of 
valve dorsally, to parallel with that plane ven- 
trally. Ends of spines trilobate, bilobate or 
pointed (Figs 3E, F). Spines absent along dorsal 
margin. Ventrally, spines separated from basal 
plane of valve by slightly flanged rim. Approxi¬ 
mately 30 spines in one row around inflated 
portion of carapace. Some spines probably miss¬ 
ing through damage to valve. Spines 2 or 3 times 
more numerous on juvenile specimens than on 
adult. Ventral marginal zone of inflated area flat 
and normal to valve plane, forming broad basal 
platform 0.2 mm across (single valve). 
Hinge-line marked in left valve by simple, 
smooth median bar with long, narrow grooves at 
anterodorsal and posterodorsal angles (Figs 2B, 
3C, D). Muscle scar pattern consisting of 5 ad 
ductors in a compressed vertical row, with 2 
small, subcircular frontal scars, one small ven¬ 
tral mandibular scar and 2 prominent dorsal 
scars (Fig. 2A). Inner margin moderately broad 
in anterior, narrow in posterior (Fig. ID), Radial 
pore canals not detected. Line of concrescence 
deviates from inner margin; vestibule moder¬ 
ately broad anteriorly, narrow posteriorly. No 
eye tubercle. Sexual dimorphism not known. 
Affinities. Miracythere sp. A differs from M. nov- 
aspecta (Figs IE, 3B) in its more rounded ends 
and its spatulate rather than “peg-like” spines 
which occur in a single row marginal to the valve 
and the inflated area, rather than in 2 or 3 rows, 
The tubercle of the present species also carries 
spines rather than the pustules found on M. 
novaspecta (Fig. 3B). Additionally, there is no 
tooth in the hinge elements of the left valve. 
Miracythere sp. A resembles the type species in 
the median vertical sulcus, the ornamentation of 
spines, the muscle scar pattern and the shape 
and appearance of the carapace in lateral view. 
These features clearly establish the species as 
belonging to Miracythere. 
Remarks. Miracythere sp. A is more closely 
allied morphologically to the Pleistocene speci¬ 
men from New Zealand (Fig. 2C) than it is to M. 
novaspecta (Fig. IE), having a similar arrange¬ 
ment of spines, a lophodont hinge structure and 
a similar subrounded quadrate shape. However, 
the Pleistocene specimen does not have a clearly 
differentiated, inflated inner lateral section of 
the valve as found in Miracythere sp. A. The 
fragmentary valve from the Late Eocene of the 
Blanche Point Formation, South Australia (Fig. 
IB) may be conspecific with Miracythere sp. A. 
The dimensions of the lost adult specimen of 
Miracythere sp. A were the same as those of the 
holotype M. novaspecta , allowing for the fact 
that the former specimen was a single valve 
whereas the latter is a carapace. It was not poss¬ 
ible to determine whether this adult valve be- 
