SILURIAN BIVALVED MOLLUSCA OF VICTORIA. 
Measurements. — Type specimen : Length, 21.5 mm.; height, 
9 mm.; number of concentric lamellar ridges measured over a 
width of 4 mm. — 5. 
Observations. — The above species is recognised by its 
depressed valves, the somewhat acutely rostrate posterior 
extremity, and the comparatively wide interspace between the 
concentric ridges. 
Affinities. — This species also shows certain affinities with 
the previously-mentioned P . muta, J. Hall, from the Hamilton 
Group of New York State. The rostrate extremity of P. 
raricostce and its depressed shape shows it to be specifically 
distinct. 
Horizon and Locality .— Silurian (Yeringian). From the 
dark mudstone at the junction of the Woori Yallock and the 
Yarra, coll. Geol. Surv. Viet., B23. In the olive-brown mud- 
stone about lfr miles below Simmons’ Bridge Hut on the Yarra, 
coll. Geol. Surv. Viet., B16. [7918 (type), 2251.] 
Palceoneilo spectabilis, sp. nov. PI. III., Figs. 51, 52. 
Description. — Shell of medium size, elongate ovate, 
rostrate; strongly convex in the umbonal region. Beaks nearly 
central, moderately well-inflated and gibbous. Cardinal line 
arcuate, gently curving to the broad anterior extremity. 
Ventral border straight, inclining posteriorly towards the 
cardinal line, and meeting the latter in a somewhat sharp curve. 
Umbonal slope forming with the median area a sinuous and 
obtuse ridge. Anterior slope gently convex. Teeth compara- 
tively stout, and not so numerous as usual in this genus ; about 
10 on the posterior side of the beak. Surface having a series 
of concentric step-like folds and lamellar ridges, with com- 
paratively fine strise in the intervals between the ridges. 
Measurements. — The type specimen: Length, 28.5 mm. ; 
height, 11.5 mm.; depth of valve, about 4 mm. 
Observations. — This species is distinguished from P. Vic- 
toria by its umbonal convexity and conspicuously rostrate 
outline. It is also a much heavier shell, and the groove for the 
external ligament is more distinctly seen. 
Horizon and Locality. — Silurian (Melbournian). In the 
blue and yellow shale of the Yarra Improvement Works, S. 
Yarra. Type presented by Mr. F. P. Spry. Also in the fine- 
grained sandstone at Moonee Ponds Creek, Flemington, coll. 
Geol. Surv. Viet., B 8. [7919 (type), 7920.] 
