THE CAINOZOIC CIDARIDAE OF AUSTRALIA. 
G. prunispinosa 
G. pentaspinosa 
G. murrayensis 
G. mortenseni 
Rather small. De- 
pressed. 
Small. Very de- 
pressed. 
Small. Very de- 
pressed. 
Rather small. 
Shape unknown. 
Non-conjugate 
pores. .. 
Non-conjugate. 
Non-conjugate. 
Non-conjugate. 
6 ambulacral plates 
adjacent to largest 
coronal plate in 
adult specimens. 
6 Plates. 
5 Plates. 
8 Plates. 
Suture in inter- 
poriferous area very 
slightly sunken. 
Sunken. 
Sunken. 
Sunken. 
Scrobicules sunken, 
elliptical, circular 
near apex. 
Sunken, circular, 
elliptical near 
actinosome. 
Slightly sunken, 
circular, elliptical 
near actinosome. 
Sunken, elliptical 
in actinal region, 
nearly circular 
elsewhere. 
No ring of tubercles 
around scrobicules. 
Margin overhangs 
latter. Tubercles 
on non-scrobicular 
portion of plate not 
numerous. 
Conspicuous 
scrobicular ring 
overhangs slight- 
ly. Tubercles on 
plate almost en- 
tirely confined to 
ring. 
Conspicuous 
scrobicular ring 
overhangs slight- 
ly. Tubercles out- 
side ring crowded. 
Conspicuous ring 
does not over- 
hang. Few 
tubercles outside 
ring. 
Interambulacral 
median area broad, 
tuberculate, not 
sunken. No pits at 
angles of plates. 
Narrow, sunken, 
bare. Pits present. 
Median area is 
crossed by raised 
ornament con- 
necting adjacent 
plates ; pits in 
between. 
Bare, sunken. 
Pits present. 
No horizontal su- 
tural groove be- 
tween two upper- 
most abactinal 
iamb plates. 
Sutural groove 
present. 
Sutural groove 
present. 
Unknown. 
Acknowledgments. 
We desire to tender our sincere thanks for the loan of speci- 
mens to C. T. Madigan, M.A., F. A. Singleton, M.Sc., and the 
Rev. George Cox ; we have also to thank Miss A. E. Baesjou 
for presenting a fine series of cidaroid spines from Booanya, 
Western Australia. 
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