SILURIAN BIVALVED MOLLUSCA OF VICTORIA. 
Pciracyclas siluricus, var. heathcotiensis, nov. PI. VI., Figs. 
86, 86a. 
Description. — Suborbicular, rounded in front, subtruncate 
behind. Beaks central, salient and subacuminate, sharper than 
in the preceding species. Valves strongly convex, especially in 
the umbonal region, where they become almost ridge-like; super- 
ficial markings in the form of fine concentric striae. 
Measurements.— Length, 13.5 mm.; height, 13.5 mm.; depth 
of valve, 4 mm. 
Observations. — This variety presents marked differences 
from the foregoing species, but in view of the fact that only 
a single example has occurred up to the present, and in associa- 
tion with the specific form, it will be safer for the present to 
regard it merely as a variety. In common with the type form, 
the figured specimen shows obscure indications of a radial 
lineation of the shell. 
Horizon and Locality. — Silurian (Melbournian). Ranges 
east of Heathcote, coll. Gfeol. Surv., Viet., B b 50. [988.] 
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