Hchinoidea — Sea-urchins. 93 



hieroglyphicus and the specimens of Pelanechinus, which appears Sea- 



to have been flexible like the recent Phormosoma. Another ^®^^^■• 



existing deep-sea type is foreshadowed by the genus Collyrites, yn^^^ 



in which the apical system of plates is broken up, much as it is East Side. 



in Pourtalesia. Wall-cases 



15-17 



The Cretaceous Echinoidea contain two distinct faunas — one Tablel 



from the Lower Greensand, and one from the Gault. Upner cases 



78-78 



Greensand, and Chalk. The former is small, but the latter is 



the most interesting in the English series. The most striking 

 feature in it is the predominance of large specimens of Cidarts, 

 of which a fine series of specimens from the Chalk is shown in 

 Table-case 77. Amongst these, reference may especially be 

 made to the example (E. 1,952) of Cidaris sceptrifera, with 



Fig. 150. — Hemicidaris intermedia, Lamk., sp., showing tubercles, the larj^er of 

 which are perforated and surrounded by an areola. Coralliau Oolite : 

 Calne, Wilts. (Natural size.) 



a, side-view of test. h, test seen from above. 



the apical plates, and those of Cidaris clavigera (33,455 and 

 39,998), which show the jaws in position and the spines at- 

 tached. Eollowing the family of the Cidarid^ comes that of 

 the Saleniid^, which is of interest as having an additional plate 

 in the apical system. 



The great family of the DrAOEiiATiD^ is represented by a largo 

 series of forms, of which CypJiosoma Koenigi, from the Chalk, is 

 the best known. The genera Glyphocyphus and Zeuglopleurus are 

 of interest as the forerunners of sea-urchins with pitted tests, 

 such as Temnopleurus. 



The specimen in the Cretaceous series which is most worthy 

 of notice is an JEchinothuria florin (m. 40,376), which is the 

 type of that genus and was the first Echinoid with imbricatmg 

 scales described from rocks later in date than the Palaeozoic. 



