Upper Silurian.] PALZONTOLOGY OF VICTORIA. [ Mollusca. 
moreland (British Paleozoic Fossils, page 320). All observers are 
now agreed that the two supposed species of Sowerby, as above 
quoted in the Reference, should be united under the present name, 
as I originally suggested. 
Common in the Upper Silurian Sandstone (Mayhill Sandstone) 
of Wenlock age, at road section, sect. 44, parish of Wallan (B") ; 
also in similar sandstone at (A1); also in sandstones of same age 
in Royal Park, near Melbourne ; rarer in (B” 20), Wenlock shale, 
near Kilmore. 
EXPLANATION OF FIGURES. 
Plate LVII.—Fig. 1, fragment, natural size. Fig. la, portion magnified, showing traces of 
striation. Fig. 2, section of larger specimen. 
Prate LVII., Fias. 3 ann 4. 
ORTHOCERAS BULLATUM (Sow.). 
DerscripTion.—Section broad oval, tapering gradually (at about the rate of 
3 lines in 2 inches from a diameter of 1} inches); septa about 1 line apart, at about 
1 inch or less in diameter; very slightly oblique; [siphon subcylindrical, moderate, 
nearly central]; surface covered with fine, rigid, nearly equal longitudinal striz, 
nearly twice their thickness apart, separated by flat spaces, about 8 in the space of 
one line. 
REFERENCE.—Sow., Sil. Syst., t. 5, fig. 29. 
There cannot be any doubt of the identity of this Australian 
species with the English one, of which I have formerly published 
(Brit. Pal. Foss.) a more minute description than that originally 
furnished by Sowerby, although the character above enclosed in 
brackets cannot be seen in our Australian fragments. When 
viewed with a longitudinal incidence of light, very faint, slightly 
convex, transverse undulations may be seen in parts which are not 
visible when the light is transverse. 
The O. Neptunianus (Bar.) from the Upper Silurian limestone 
of Bohemia is very nearly allied, but has the septa much wider 
apart and the striae closer, and less regular as I find on comparison. 
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