62 
M. T. WARNE 
Dimensions. LV, NMV PI22190: L = 0.36 mm, H = 
0.29 mm; LV, NMV P122191: L = 0.36 mm, H = 
0.29 mm; RV, NMV P122192: L = 0.37 mm, H = 
0.30;juvenile RV, NMV P122193: L = 0.24 mm, H = 
0.19 mm. 
Polycope melbournensis sp. nov. 
Figs IB, 2E-F 
Polycope sp. 1.—Warne 1987: 441, pi. 1, fig. B. 
Polycope sp. 5.—Warne 1987: 441. 
Etymology. A reference to the city of Melbourne, situ¬ 
ated in the northern part of the Port Phillip Basin. 
Holotype. Adult LV, NMV PI22194 from the 
Fyansford Formation (Middle Miocene, Balcombian) 
at mid tide level, Fossil Beach, Mornington, Victoria, 
approximately 200 m north of end of driveway down 
to beach; 38°14'S, 145°02'E. 
Paratype. Adult RV, NMV PI22195. 
Additional material. Fifty-one disarticulated adult and 
juvenile valves from the Fyansford and Sherwood For¬ 
mations. 
Dimensions. Holotype, LV, NMV PI22194: L = 0.55 
mm, H = 0.46 mm; paratype, RV, NMV PI22195: L 
= 0.52 mm, H = 0.47 mm. 
Diagnosis . Carapace moderately large, with 
loosely ordered reticulum and prominent an¬ 
terior and anteroventral marginal rib parallel to 
free margin. 
Description. Carapace thin-shelled, inflated 
posterodorsally. RV larger than LV, both valves 
more or less circular in shape. RV with a very 
weakly developed anterior rostrum, not evident 
in LV. Dorsal margin short, slightly arched in 
RV, straight in LV; posterior margin of both 
valves evenly rounded; anterior margin straight 
in anteroventral region of RV. In dorsal view 
both valves slightly swollen posteriorly, Maxi¬ 
mum length at mid-height; maximum height at 
mid-length; maximum width slightly posterior 
to and above mid-height. Low relief ornament 
covering most of carapace, consisting of pen¬ 
tagonal reticulae on periphery and a distinct 
anterior and anteroventral marginal rib parallel 
and close to free margin. Normal pore canals 
large, simple and scattered. Inner lamellae nar¬ 
row with inner margin parallel to outer margin. 
No vestibule visible; marginal pore canals seen 
in posterior region are numerous and straight. 
Hinge simple, smooth and adont. A series of 
small anteroventral denticles present on both 
valves. Adductors consisting of a cluster of three 
scars at maximum width of carapace. Sexual 
dimorphism not conspicuous though some 
adults are very slightly more inflated than others 
and these may be females. 
Remarks . Differences in the degree of ornamen¬ 
tal relief in P. melbournensis were originally 
interpreted by me (Warne, 1987) as indicating 
the presence of two different species, but these 
differences seem to be due to either eco- 
phenotypic or taphonomic factors. P. melbour- 
nensis is similar to P. reticulata Muller, 1894 but 
the latter is slightly different in shape and has a 
more strongly developed and irregularly shaped 
reticulum. P. cancellea Hartmann, 1954 is 
smaller and possesses a less evenly rounded 
lateral outline. Pseudopolycope intermedia 
(Chavtur, 1979) has a more angular dorsal mar¬ 
gin and lacks a marginal ridge. Pseudopolycope 
krytatcki (Chavtur, 1977) differs in having a 
lateral protuberance, whereas Pseudopolycope 
comandorica Chavtur, 1979 is larger and has a 
more clearly defined rostrum. The similarities 
between Polycope melbournensis and the last 
three species suggest, however, that the new spe¬ 
cies may be referred ultimately to Pseudopoly 
cope. 
Age and stratigraphical range. Specimens range 
in age from late Early Miocene (Batesfordian, 
foraminiferal zones N7/8) to late Middle or early 
Late Miocene (late Bairnsdalian or Mitchel- 
lian?), occurring in marls, clays and sands of the 
Fyansford and Sherwood Formations. 
Remarks. This species is very similar to Polycope 
sp. 1 Whatley & Downing, 1983 (= Polycope sp. 
3 Warne, 1987) but there are minor differences 
in size, ribbing and reticulation. The possibility 
that the two forms are variants of the one species 
is not excluded. Polycope demulderi Sissingh, 
1972 and the species illustrated by Puri & 
Hulings (1976) as Polycope? favus Brady, 1880 
(although somewhat different from the illus¬ 
tration of this species in Brady’s monograph) are 
probably closely related forms because of their 
similar shape and ornamental pattern. Chavtur 
(1981) tentatively included P. demulderi in his 
genus Archypolycope which is, however, defined 
on soft part anatomy (see discussion of family 
above). 
Age and stratigraphical range. Recorded only 
from the early Middle Miocene (Balcombian to 
early Bairnsdalian, foraminiferal zones N8/9- 
N10/11) clays of the Fyansford and Sherwood 
Formations. 
