aENEBA AND GBOUPS OF THE ECHIirOIDEA. 33 



Spines variable, either long, cylindrical, and pointed, tlie sur- 

 face having thorns, pointing irregularly outwards, or short, stout, 

 cylindrical or flat in outline, with enlarged cup-like tops with a 

 fringe of strong radiating spinules ; spinules in vertical series 

 along the stems or restricted to the edge, in the flat specimens. 



Viviparous, unisexual. 



Fossil. Tertiary : Sind, Asia. 



Recent. Philippines ; Indian Archipelago ; East Indies ; Aus- 

 tralia, jN". South Wales ; Tasmania ; Falkland, Marion, and Ker- 

 guelen Islands ; Patagonia ; Antarctic Ocean ; Natal ; Zanzibar. 



"Wy. Thomson and Studer discovered about the same time, in 

 1876, that Goniocidaris was viviparous, and that the young were 

 carried upon the apical system, protected by the upper spines of 

 the test, until their full development took place. Studer, 1876, 

 Berl. Akad. Monatsb. p. 455, noticed the large genital openings 

 covered by a thin membrane ; and Thomson described the method 

 of carrying the young, and that the female genital openings 

 notch the edge of the basal plates (Journ. Linn. Soc. vol. xiii. 

 1876; and Voyage of the ' Challenger,' vol. ii. p. 228). It is 

 necessary to admit the unisexual nature of the species*. 



G-enus Orthocidaeis, Gotteau, 1862, Pal. Frang., Terr. Gret. 

 vol. vii. p. 364. 



Syn. Hypodiadema, Desor (pars). 



Test moderate and subspherical. 



Apical system flush, pentagonal, small. 



Ambulacra narrow, straight ; interporiferous area with small 

 granules, which may have mamelons, placed in several rows and 

 without order ; pairs of pores in simple straight series, the pores 

 separated by a granule, in low primary plates. 



Interradia very broad, plates numerous ; primary tubercles very 

 small, perforate and plain, distant, occupying a small portion of 

 their plates ; the scrobicules small and circular ; the miliary areas 

 large, and the granules with mamelons. 



Peristome small, narrow, without branchial incisions ; the 

 interradial lips the largest. 



Fossil. Lower Cretaceous : Europe. 



* Genus Biscocidaris, Doderlein, from Japan, has large outer anal plates and 

 disciform ends to the primary spines; and it is a Cidaris. Anaulocidaris, Zittel, is 

 too close to Cidaris to be considered otherwise than a species. 



Schleinitzia, Studer, is a Cidaris. 



Eocidaris, Eeyserl., now appears to have all the requisite structures to classify 

 it with Cidaris, and thus the genus is carried back in time to the Permian age. 



LINN. JOUEN. — ZOOLOGY, VOL. XXIII* 3 



