THE CAINOZOIC CIDARIDAE OF AUSTRALIA. 
Genus PHYLLACANTHUS Brandt, 1835. 
(Synonym : Leiocidaris Desor, 1855.) 
This genus has primary spines cylindrical or terete, sometimes 
with a series of small serrations but never with thorns or pro- 
jecting ridges. The pores are conjugate. (Clark, H.L. 1925). 
Mortensen (1929) has recently listed five of the six known 
living species of this genus as inhabiting Australian seas ; he 
states that Phyllacanthus must be restricted to those species 
which have thick, smooth, cylindrical spines. Living species 
are littoral. Duncan (1877, p. 45) refers to the possible occur- 
rence of Phyllacanthus in our strata. Spines from Miocene 
deposits of India and of Madagascar probably belong to this 
genus (Mortensen, 1929). P. javanus Martin occurs in the 
Miocene of Java (Martin, 1883-7) and Yule Island, Papua 
(Chapman and Crespin in Montgomery, 1929-30). Miss Currie 
(1930) has figured some spines from Late Tertiary beds of Kenya, 
East Africa. 
Phyllacanthus duncani sp. nov. 
Leiocidaris sp. nov., Duncan, 1887, Q.J.G.S., vol. 43, p. 412. 
Plate XII, figs. 7-9 ; Plate XV, fig. 33. 
Duncan’s description of Leiocidaris sp. nov. is as follows : — 
“The ambulacrum is rather undulating and narrow ; the poriferous zone 
is very slightly sunken ; the pores are large ; the outer one of a pair is the 
larger and elliptical ; the inner or adoral is round ; they are united by a 
groove, and about seventeen pairs are in relation to a large interradial coronal 
plate. Interporiferous area with a row of small, imperfect secondaries, with 
slightly raised scrobicules and a small boss, no mamelon, placed close to the 
poriferous zone, and a series of smaller secondaries nearer the median line, in 
a vertical row extending along the middle of the area, but not reaching much 
actinally or far towards the apex. The primaries of the interradia are large ; 
the scrobicules are distinct, nearly circular, and there is a row of small second- 
aries and a few granules between them and the horizontal sutures of the plates. 
The boss is broad at the base and conical, and the mamelon is contracted at 
the neck and is perforated. There is no crenulation. The margin of the 
scrobicular circle is sunken, and is surrounded by a row of small secondaries 
made up of an elongated raised scrobicule, longest transversely, and a small 
boss ; there are a few smaller tubercles placed beyond the circle, and fitting 
in between the larger, so as to complete the circle, and a few exist beyond it. 
Two or three rows of still smaller tubercles extend along the plates beyond the 
circle towards the median line, and the median area of the interradium is 
narrow. Numerous spines are in the collection, and the large and nearly 
smooth ones may be associated with this genus.” 
Observations. — We have named this form after the late 
Prof. P. M. Duncan, whose description we have quoted above, 
and have referred it to Phyllacanthus , of which Leiocidaris is a 
synonym, being guided partly by the nature of the spines. 
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