88 HEMICIDARIS. 



Hemicidaris Bravenderi and Hemicidaris intermedia apply with equal truth as between 

 our species and Hemicidaris crenularis, which differs from Hemicidaris intermedia chiefly 

 in the form of its spines. The test is now figured in detail and described for the first 

 time. I dedicate the species to Mr. Bravender, F.G.S., of Cirencester, who first found 

 this urchin in 1844, at Stratton, near Cirencester, and to whom I am indebted for the 

 loan of the original specimen with spines, figured in PI. XI, fig. 3. 



Hemicidaris Wrightii, Desor. PI. V, fig. 2 a, b, c, d, e. 



Hemicidakis alpina. "Wright, on the Cidaridse of the Oolites, Annals and Magazine of 



Natural History, 2d series, vol. viii, p. 256, pi. II, fig. 3 a, h. 



— — Forbes, Memoirs of the Geological Survey, Decade III, pi. 5. 



Notes on British Species of Hemicidaris. 



— — Morris, Catalogue of British Fossils, 2d ed., 1854, p. 81. 



— Weightii. Desor, Synopsis des Echinides Fossiles, p. 54. 



Test sub-globose, depressed above ; ambulacral areas prominent, convex, and slightly 

 flexuous, crowded with four rows of small mihary granules on the sides, and four semi- 

 tubercles at the base ; primary tubercles of the inter-ambulacral areas suddenly diminishing 

 in size above ; apical disc large, prominent, and convex. 



Dimensions. — Height, nearly three fifths of an inch ; transverse diameter, nine tenths 

 of an inch. 



Description. — When this beautiful urchin was discovered some years ago, I pro- 

 visionally identified it with Hemicidaris alpina, Agassiz, from the peculiar structure 

 of the ambulacral areas. Finding that my friend Mr. S. P. Woodward had made a 

 like determination of a specimen contained in the collection of Mr. Lowe, and obtained 

 from the same locality, I figured and described it as Hemicidaris alpina, with this 

 remark : " I consider my urchin, however, merely a variety of the Swiss species, for 

 which I propose the name variety c/ranularis." My late lamented friend. Professor Edward 

 Forbes, had formed a similar conclusion from the specimens he examined, for he observes, 

 in his notes on the species of Hemicidaris found in British strata, Hemicidaris alpina, 

 Agassiz — " A pretty species, easily distinguished from its congeners by the very small and 

 thickly-set ambulacral tubercles." M. Desor's knowledge of the type of Hemicidaris 

 alpina, Agassiz, enabled him to point out the distinctive characters between that species 

 and our urchin. He says — " Hemicidaris Wrightii, Desor. Syn. Hemicidaris alpina, var. 

 granularis, Wright. Les ambulacres sont plus saillants et moins larges que dans le 

 Hemicidaris alpina ; leur rangees externes de granules sont moins accusees. Sur contre il 

 existe a I'interieur de ces granules margin ales quatre a six rangees de tres fines granelures 



