SILURIAN BIVALVED MOLLUSCA OF VICTORIA. 
The original is an impression of a left valve in blue mud- 
stone, and the drawing has been made from a well-defined cast 
in wax. 
Observations. — The above fossil is a typical Aviculopecten, 
in accordance with the emended definition of the genus given by 
J. Hall,* since it has a short hinge-line and well-defined ears. 
Horizon and Locality. — Silurian (Melbournian). Yarra 
Improvement Works, S. Yarra; presented by Mr. F. P. Spry. 
[7940.] 
Family Modiolopsidae. 
Genus Modiolopsis, J. Hall, 1847. 
Modiolopsis melbournensis, sp. nov., PI. V., Figs. 76, 7 6«. 
Description. — Shell small, sub-quadrate, elongate, com- 
pressed posteriorly; length rather less than twice the height. 
Cardinal line nearly straight; ventral margin parallel. 
Anterior extremity narrowly rounded, and incurved under the 
prominent sub-anterior beaks. Posterior extremity broadly 
rounded, and meeting the hinge-line at an obtuse angle. 
Umbonal ridge extending from the beaks to near the postero- 
ventral angle. Greatest convexity of surface in the umbonal 
region; ventral area somewhat depressed. Surface marked by 
fine, irregularly concentric growth-lines. 
Measurements. — Length, 16 mm.; height, 9 mm. 
Affinities.— A form nearly allied to the above is Modiolopsis 
solenoides, Sowerby, sp.f, from the Upper Ludlow, near Bridge- 
north, England. It differs from our species, however in Its 
greater compression, less prominent beaks, and in having a 
broad median depression in the ventral region. 
Horizon and Locality.— Silurian (Melbournian). Yarra 
Improvement Works, S. Yarra. [7941.] 
Modiolopsis complanata, Sowerby, sp. PI. V., Lig 77 
Pullastra complanata, Sowerby, 1839, in Murchison’s 
Silurian System, p. 609, PI. V., Fig. 7. 
Modiolopsis complanata, Sow. sp., McCoy 185^ Brit Pol 
Foss., p. 266. J ’ ai- 
*Pa 1 . N. York, Vol. V., Pt. I., 1884, Lamell. I., p XII 
t Siluria, 3rd ed„ .859, 1 < 1 . ,3, Fig. 9 [" Orthonota ( ICypicardia) solenoides ”]. 
[ 50 ] 
