Mem. Nat. Mus. Vict., viii, 1934. 
THE CAINOZOIG CIDARIDAE OF AUSTRALIA. 
By Frederick Chapman, A.L.S., F.G.S., Commonwealth Palaeon- 
tologist, and Francis A. Cudmore, Hon. Palaeontologist, 
National Museum. 
Plates XII-XV. 
Nearly 60 years ago Professor P. M. Duncan described the 
first Australian Cainozoic cidaroid before the Geological Society 
of London. During the next 20 years Professors R. Tate and 
J. W. Gregory published references to our fossil cidaroids, but 
further descriptive work was not attempted until the present 
authors undertook to examine the accumulated material in the 
National Museum, the Tate Collection at Adelaide University 
Museum, the Commonwealth Palaeontological Collection, and 
the private collections made by the late Dr. T. S. Hall, F. A. 
Singleton, the Rev. Geo. Cox and the authors. 
The classification of the Cidaridae is founded mainly upon 
living species and it is partly based on structures which are 
only rarely preserved in fossils. Fossil cidaroid tests are usually 
imperfect. On abraded tests the conjugation of ambulacral 
pores is obscure. The apical system is preserved only in one 
specimen among those examined. The spines are rarely attached 
to the test and pedicellariae are wanting. Therefore, in dealing 
with our specimens we have been guided mainly by the appear- 
ance and structure of ambulacral and interambulacral areas. 
Certain features used in our classification vary with the growth 
stage of the test : for instance, the number of coronal plates in 
vertical series, the number of ambulacral plates adjacent to the 
largest coronal plate, and sometimes the number of granules on 
the inner end of ambulacral plates. 
In the collections before us only one test has the spines still 
attached ; in another specimen, the test and a spine are only 
slightly separated ; and in a third a group of spines was closely 
associated in a block of marly limestone though the test was 
not collected. 
Where the evidence warrants it, we have suggested that 
cidaroid tests and generically related unattached spines found 
in the same layer belong to the same species. Original colour 
markings of spines are sometimes recognisable, especially when 
specimens are thinly varnished ; this is a detail of some import- 
ance, since that feature is used in classifying recent cidaroids. 
Some spines, as in living examples, are encrusted with growths 
of parasitic polyzoa. 
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