741 
8. LEPTiENA suBJiiQUicosTATA, L. G. de KonincJc. 
PI. Ill, fig. 2. 
Shell almost as long as broad, of snbsemi-elliptic shape ; ears slightly 
curved on themselves, and ending in almost a right angle. Ventral valve 
fairly regularly arched ; beak small, slightly incurved, not prominent ; area 
narrow ; fissure triangular, with a very wide base completely closed by the 
cardinal process of the dorsal valve. This [dorsal valve] is concave and follows 
the curvature of the ventral valve, leaving hut a small space between the 
two. The outer surface of each valve is ornamented with small radiating 
almost smooth ribs, which are separated from one another by a small furrow ; 
towards the middle of the shell these ribs increase by forking, and thus pre- 
serve an almost equal thickness through their whole length. The internal 
structure of the valves is unknown to me. 
Dhnensions. — Length, twenty-six millimetres ; width, thirty milli- 
metres ; thickness, about two millimetres ; number of ribs at the margin 
about seventy. 
Belations and Differences. — In general form this species resembles 
certain varieties of S. compressa, Sow.,^ and that of S. {Leptcena) ohscura, 
J. Hall," from which it dilfers in its greater convexity, and in the number 
and form of its ribs. 
Horizon and Locality. — A single specimen of this species has been 
found in a black Devonian limestone from near Yass. 
PENTAMEPtUS, Sowerhy. 
Pentamertjs pumilus, L. G. de Koninch.^ 
PI. Ill, fig. 3. 
This little shell is slightly transverse, snbglobose. The ventral valve 
is rather regularly arched ; the beak small, although rather strongly incurved, 
projects a little beyond the hinge line ; the outer surface is ornamented with 
fifteen slightly angular folds, sharply separated from one another by deep 
furrows ; all these folds commence at the beak and continue to the edge without 
bifurcating ; of these folds, the mesial is a little stouter than the others ; it 
^ Davidson, Sil. Bracli., pi. 46, fig. 11. 
2 J. Hall, Pal. N. York, ii, pi. 31, fig. 2. 
2 [ Vide E. Etheridge, Junr., Kecords Geol. Survey N. S. Wales, 1892, iii, Pt. 2, p. SO.—W.S.D.] 
