100 
ON THE OCCURRENCE OF THE GENUS PALCEASTER 
IN THE UPPER SILURIAN ROCKS OF VICTORIA. 
By R. Etheridge, Junr. 
(Plate xxx.) 
The Upper Silurian rocks of Victoria have so far yielded two 
species of Asteroidea, and one well defined species of Ophiuroidea, 
whilst a second doubtful species of the latter class is believed to 
exist. The former are Petr aster Smytliii , McCoy,* from the 
Moonee Ponds beds, and Ur aster ell a Selwynii , McCoy, f from near 
Kilmore. The single described species of the second class is 
Protaster brisingoides , Gregory, j from Moonee Ponds, the doubt- 
ful one being a MS. name Tceniaster australis , McCoy. It has 
been suggested that this is merely a synonym of Gregory’s P . 
brisingoides. 
In the genus Palceaster , Hall, the structure of the arms on the 
actinial side consists of two rows of ambulacral plates, and two 
rows of adambulacral plates, bordered on each side by a row of 
marginal plates. In Urasterella, McCoy, adambulacral plates are 
present as in Palceaster , but marginal plates do not exist. In 
Petr aster, Billings, on the other hand both adambulacral and 
marginal plates are developed, but separated by a row of disc 
plates ; while in Palasterina , the disc itself is much extended, and 
the adambulacral plates in the interradial angles are large and 
triangular. 
I now purpose describing a star-fish in the Museum Collection, 
from Moonee Ponds, which certainly appears to have the structure 
of Palceaster , Hall, rather than that of either of the genera named. 
Palceaster meridionalis, sp. nov. 
(PL xxx., fig. 16 & 17.) 
Sp. Char . — Body small; rays moderately long and rather acutely 
pointed, fifteen millimeters from the actinial centre to the apices; 
interbrachial angles broad and obtuse ; abactinial surface unknown. 
Ambulacral avenues wide in comparison to the size of the body, 
deep, very gradually tapering, the sides more or less straight 
walled ; ambulacral plates about twenty in number on each side, 
transversely oblong, bearing more or less pyriform pores ; adamb- 
ulacral plates quadrangular, smaller than the marginal plates, 
placed along the prominent edges of the ambulacral avenues; 
# Prod. Pal. Viet., Dec. I., 1874, p. 41, t. 10, f. 1. 
f Ibid, p. 42, t. 10, f. 2 and 3. 
j Gfeol. Mag., 1889, vi. (3), p. 24. 
Dec., 1891. 
