EcuiInoDERMATA. | UPPER PALAZXOZOIC RADIATA. 125 
rocks or existing seas. In these latter it would of course be impossible to divide the test at the suture into five 
equal parts, and the name I have proposed refers to the comparative complexity of their structure. 
On the same grounds that the Order Echinidw is divided into the families Echinidw and Cidarida, this 
might be divided into the families Palechinide and Archeocidaride—the first of both families having imper- 
forate spiniferous tubercles of one kind, the 2nd family of each order having numerous small secondary tubercles 
and few large primary ones, perforated for the /igamentum teres of the spine. 
Genus. ARCHAOCIDARIS (A/°Coy). 
Ref—M'Coy, Synopsis Carb. Foss. Irel. p. 173, and Ann. Nat. Hist. 2nd Series, Vol. III. p. 252. 
Gen. Char-—Interambulacra of three or more rows of plates bearing each one large, mammillated, 
perforated, primary tubercle surrounded by an elevated ring, round which the small secondary tubercles are 
scattered ; primary spines very large, resembling those of Cidaris in form. 
ARCHAOCIDARIS VETUSTA (Phill. sp.) 
Syn. and Ref.—Cidaris vetusta Phil. Geol. York. Vol. II. p. 208. 
Prof. Phillips gives no detailed description, nor figure of his ©. vetusta, and I have little doubt it is iden- 
tical with the previously described C. Urii (Flem.), and the subsequently described C. Benburbensis (Portk.) ; 
I have however used his specific name here to designate a fragment of a primary spine, and its supporting plate 
in the collection from the Derbyshire limestone, which may perhaps be distinguished from the A. Urii by the 
generally smaller size, and the more delicate, thorn-like denticles of the spine. 
