Upper Silurian.] PALHONTOLOGY OF VICTORIA. [Moltusca, 
the receiving valve, the beak of which is large and incurved, very narrow in the opposite one, 
the beak of which is small; shell structure fibrous; foramen notching the area of both valves, 
that of the entering valve open, that of the receiving valve with an internal pseudo-deltidium 
bordered by two strong diverging dental lamella in the receiving valve, and by the flattened 
bases of the spiral apophyses in the other, which also usually shows a small mesial septum. | 
Description.—Rhomboidal, wider than long, hinge-line usually shorter than 
width of valves; cardinal angles obtusely rounded ; cardinal area moderately wide 
in each valve; valves moderately convex; mesial fold large, rounded, flattened 
towards the margin with two (or a trace of a third) large rounded ribs on each side, 
sometimes distinct to the hinge-line, at others only waving the margin. Surface 
with fine longitudinal strize (about nine in 1 line at 6 lines from beak) alternate near 
the margin and crossed by lines of growth. Average width, rather over 13 inches; 
proportional length, 56%, ; depth of both valves, 60. 
REFERENCE.—Conrad, An. Rep. Pal., N. York, 1840. Hall, Pal. New York, 
vol. 3, t. 27. 
There can be no doubt of the identity of our Australian fossil 
and the S. macropleura of the American geologists from their 
“Lower Helderberg” rocks of New York, which are of the same age 
as the Wenlock formations of English writers, but I greatly doubt 
the propriety of separating it specifically from the S. eyrtena (Dal.) 
(or S. plicatella (Lin.), as many writers prefer to call it now) typical 
specimens of which from Sweden are so variable as to show all the 
characters of S. macropleura on a somewhat reduced size. 
Common in the Wenlock shale (B’ 22) near Kilmore (N.E.). 
EXPLANATION OF FIGURES. 
Plate XLVI.—Fig. 7, view of internal cast of receiving valve, natural size. Fig. 7a, rostral 
view of same specimen, showing cardinal area. Fig. 7b, magnified portion of surface of cast, 
showing lines of reticulo-punctation. Fig. 8, entering valve, imperfect on both sides, natural size. 
Pratt XLVL, Fias. 9, 10. 
SPIRIFERA SULCATA (Hr1s.). 
DescripTton.—Transversely rhomboidal, wider than long; hinge-line exceeding 
the width of the shell, cardinal angles usually acutely pointed; valves very convex, 
receiving one much larger and more convex than the other, with a large incurved 
beak and a very deep wide concave mesial hollow bounded by two very prominent 
rounded ribs, with two to six ribs on each side (usually three); entering valve smaller 
and flatter, with a very large prominent flattened mesial ridge, with usually three ribs 
on each side; cardinal area wide and concave, but variable. Surface crossed with 
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