SILURIAN BIVALVED MOLLUSCA OF VICTORIA. 
Nuculites subquadratus, sp. nov. Pl. I1., Figs. 26, 27, 27a. 
Description.—Shell of medium size, subquadrate in out- 
line, narrower anteriorly; the ventral border broadly curved and 
truncated towards the postero-cardinal angle. Beaks rather 
prominent, situated sub-anteriorly and directed forward. 
Anterior buttress impression commencing just in front of the 
beak, curving slightly, and traversing about two-thirds of the 
distance to the ventral margin. Posterior adductor impression 
strong. Surface highly convex; median area near the beaks 
depressed, curving evenly to the ventral margin, rather steep 
toward the postero-ventral angle, presenting a decided umbonal 
slope; depressed immediately below and in front of the beaks. 
Shell-surface ornamented with closely-set, concentric lines of 
growth, and crossed by fine striae, which apparently radiate from 
the umbo, becoming stronger towards the ventral margin. 
Measurements.—(1) Length, 11.5 mm.; height, 9 mm. (2) 
Length, 6 mm.; height, 5 mm. 
Observations.—Vhis species is unusually short, and reminds 
one of Arca in its squareness. The two specimens figured, 
although differing somewhat in details, are referred to the 
same species, as they agree in their essential features. 
In N. subquadratus we have a surface ornamentation similar to 
that seen in some of the better-preserved British specimens of 
N. coarctatus, this feature of the radiating striz apparently 
being confined to these two species. 
A ffinities—The present species very closely approaches N. 
nyssa, J. Hall,* from the Hamilton Group of N. America, but 
the latter form is not marked with radiating striz, nor is it so 
quadrate in outline. 
Horizon and Locality.—Silurian (Melbournian). North of 
Yan Yean; coll. Geol. Surv., Vict., B® 11; west of Mount Dis- 
appointment, G.S.V., Bb 17. [7892 (type), 977.] 
Nuculites jutsoni, sp. nov. PI. IL., Fig. 28. 
Description.—Valves ovately elongate, length nearly twice 
the height. Ventral margin evenly curved; cardinal line slightly 
arched. Beaks sub-anterior, tumid; anterior extremity broadly 
rounded and compressed beneath the beaks; posterior extremity 
narrow, produced, curving upward and forward to meet the 
cardinal line obtusely. Deepest part of the valve just behind 
the anterior third. Surface somewhat steeply inclined in front 
* Pal. N. York, Vol. V., Pt. I., 1885, Lamell. II., p. 328, Pl. XLVII., Figs. 29, 30. 
pear 4] 
