228 
Helations and Differences. — This species could easily he mistaken for 
an Aphanaia u'ithout the equality of the valves, so much does it resemble it 
hy its external ornamentation ; it is allied to M. pernella, Ryckholt. It differs 
in its proportions and dimensions, and the much greater number of its external 
concentric folds. 
Horizon and Localities . — An internal cast of M. Bigshyi was found in 
a yellowish micaceous sandstone at Branxton. 
AVICULOPEOTEN, F. McCoy. 
Aviculopecten leniusculus, J. Dana. 
PI. xxr, Pig. 3. 
Decten leniusculus, J. D. Dana, 1849, Geol. Wilkes’ U.S. Explor. Expect, p. 704, pi. 9, fig. 6. 
This is a large, plano-convex, orbicular shell. A large part of its 
surface is nearly smootli. The surface ornamentation consists of thin, radiating 
ribs, rather irregular towards the margins ; the ribs of the right valve are a 
little thicker than those of the left. The beak of the right valve is suhmedian 
and straight. The ears are large, suhequal, striated longitudinally and waved 
transversely. 
Dimensions.— T \\q length and breadth are thirteen, and the thickness 
about two centimetres. 
Relations and Differences. — This species is remarkable for its large 
size, and seems to bear some resemblance to A. concamis, McCoy, from which 
it differs hy having no radiating folds on a large part of its surface, and hy 
its more transverse form. 
Horizon and Localities . — It was found in the Illawarra Eistrict by 
Mr. J. D. Eana, and in a calcareous conglomerate at Mt. Gimhela hy Mr. 
W. B. Clarke. 
Avictjlopecten stjbquinquelineata, F. Me Coy. ^ 
PI. XXII, Pig. 2. 
Fecten Sllb-5-lincatlls, McCoy, 1847, Ann. Mag. Xat. Hist., XX, p. 298, pi. 17, fig. 1, 
This shell is large, broader than long, transversely suboval, and 
inequivalved. The right valve is more convex than the left valve, which, 
‘ [R. Etheridge, Junr., Procs. R. Phys. Soc. Edinb., 1880, V, p. 297, t. 15, f. 52; Geol. and Pal. Q’land., 
1892, p. 266.— W.S.D.] 
