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ECHINODERMATA— ECHINOZOA 



PHYLUM IV 



Family 1. Cidaridae Gray. 



JFith characters of the order. 



The apical disk is rare in fossil Cidarids (Fig. 368, A); when preserved, the 

 ocular plates are typically all exsert. The same condition exists in the young 

 of Recent species and often in adults. When oculars reach the periproct, 

 they do so in the sequence Y, I, IV, II, III, or V, I, IV, III, II. Young 

 Cidarids approach Bothriocidaris closely in many structural details. De- 

 vonian (?), Lower Carboniferous to Recent ; maximum in Jura and Cretaceous. 



Section A. Ambidacral pore-pairs uniserial. 



Miocidaris Doderlein. Ambulacral and interambulacral plates imbricating. 

 Two Paleozoic species, M. keyserlingi (Geinitz), from the Permian of Europe, 





Fig. 378. 



Cidarls coronata Qoldt. Upper Jura (-y) ; Hossingen, Wurtemberg. A, Dorsal aspect of test with perfectly 

 preserved apical system. B, Profile. '', Portion of Amh, magnified. D, Partially restored view with spines 

 attached. 



and M. cannoni Jackson, from the Lower Carboniferous of America, are the 

 only certain Paleozoic representatives of the order. Several species in the 

 Trias and Jura of Europe. 



Cidaris Leske, ex Klein (Figs. 368, ^ ; 378-380). Amb undulating or nearly 

 straight, the pores variable in their distance, and united by a groove or not. 

 lArnh coronal plates five to fifteen in each column. Apical system large. 

 Primary spines very variable, even in the same species. Trias to Recent ; 

 chiefly Jurassic and Cretaceous. 



Of this genus more than 200 species have been described. These are grouped into seven 

 or eight artificial divisions, which are regarded by some as of sub-generic, or even generic 

 importance. Some of the groups may be briefly noticed as follows : — 



