THE CAINOZOIC CIDARIDAE OF AUSTRALIA. 
Synopsis of Species. 
St. australiae 
Ph. duncani 
Pr. scoparia 
Ch. clarkii 
Test small to me- 
dium. Abactinally 
depressed, actinally 
greatly depressed. 
Medium to large. 
Slightly abactin- 
ally depressed. 
Large. Slightly 
abactinally de- 
pressed. 
Rather small to 
large. Somewhat 
depressed. 
Non-conjugate 
pores. 
Conjugate. 
Conjugate. 
Conjugate. 
1 2 ambulacral plates 
adjacent to largest 
coronal plate in 
adult specimens. 
17 Plates. 
15 Plates. 
10 Plates. 
Ambulacra narrow, 
slightly wavy; 4, 6, 
or 8 vertical rows 
of miliaries in inter- 
poriferous areas. 
Undulating, nar- 
row ; 4, 6, or 8 
rows of miliaries. 
Undulating, nar- 
row ; 4, some- 
times G, rows of 
miliaries. 
Broad, nearly 
straight; 6 rows 
of miliaries. 
Scrobicules deeply 
sunken (variable) ; 
slightly elliptical 
below ambitus, 
otherwise circular. 
Sunken, elliptical, 
becoming circular. 
Shallow, elliptical 
at ambitus, cir- 
cular near apex. 
Sunken, ellipti- 
cal, circular near 
apex. 
Scrobicular ring 
overhangs ; incon- 
spicuous. 
Not overhung ; 
ring conspicuous. 
Not overhung ; 
ring conspicuous. 
Slightly over- 
hangs ; ring con 
spicuous. 
Interambulacral 
median area broad 
(narrow in young 
specimens); sunken. 
Broad ; only 
slightly depressed 
at suture. 
Very narrow; only 
slightly depressed 
at suture. 
Broad, flat. 
Pits and grooves at 
horizontal sutures 
between coronal 
plates. 
No pits or 
grooves. 
No pits or 
grooves. 
No pits or 
grooves. 
Perforate mamelons 
usually absent from 
abactinal coronal 
plates ; 1-5 in each 
iamb series. 
Never more than 
one rudimentary 
non - perforate 
mamelon in each 
iamb zone. 
Ditto. 
Ditto. 
[ 144 ] 
