BRITISH 



FOSSILS. 



Dega.de v. Plite II. 



DIADEMA PSEUDODIADEMA. 



[Genus DIADEMA. Grat, 1835. (Sub-kingdom Eadiata. Class Echinodermata. 

 Order Echinida. Family Echinidse.) Body circular, rather depressed ; ambulacral areae 

 with two rows of primary perforate tubercles as large, or nearly as large, as those of the 

 interambulacra ; the latter with 2 or 4 rows of primary perforate and crenulated 

 tubercles ; spines long, cylindric, striated, and annulated.] 



Diagnosis. D. 2-3 uncialis, hemisphcBrica^ depressa, tubercuUs nume' 

 rosis regulariter radiata ; primariis in utrdque area hmis, in ambulacro 

 minoribus (in singula serie circa 20) in spatio altera majoribus {circa 17), 

 secundariis parvis graiiulisque interpositis : disco anali parvo, rosacea. 



Synonyms. Cidarites pseudodiadema, Lamarck (1801), Anim. sans 

 Vert., 1st edit, t.iii. p. 59. No. 17. ; 2nd edit. 1840, vol. iii. p. 385. Cidaris 

 monilipora, Phillips (1829), Geol. Yorks., 1, 156. Cidaris diadema, 

 Young and Bird (1822), Geol. Survey of Yorkshire, t. 6. f. 3. Diadema 

 Lamarckii, Desmoulins (1837), Tab. Synopt., p. 316. No. 18. (sec. Wright). 

 D. ambiguum, ib., p. 316. (^sec, Agass. and Desor). D. pseudodiadema, 

 Agassiz (1840), Echinod. Suisses, t. ii. p. 11. tab. 17-49, 50, 52, 53. 

 Agassiz and Desor (1846), Cat. Rais. des Ecli., Annales des Sc., 3rd ser. 

 vol. vi, p. 349. Wright (1851), Ann. Nat. Hist., vol. viii. p. 271. [t. 12. 

 f. 1.] CoTTEAU (1852), Etudes sur les Ech. Foss. Yonne, p. 142. pi. 17. 

 fig. 1. [^icon mala.l 



{Diadema hemisphcericum, Ag. Pro dr. p. 22. Cot. Ecli. foss. p. 139, 

 tab. xvi. fig. 5-9 ?) Pseudodiadema hemisphcericum, Desor (1855), 

 Synopsis, p. 68. 



Of this beautiful Oolitic urchin, which is not uncommon in the 

 Coral Rag, we have had the opportunity of figuring good specimens, 

 through the kindness of Dr. Wright and Professor Morris. It is an 

 excellent example of the genus, which has a great vertical range. 

 Species of Diadema are found in all the secondary and tertiary 

 formations, and others are still living in the Mediterranean, and in 

 tropical seas. 



The genus, constituted by Dr. Gray for the Cidaris diadema 

 of Lamarck (Diad. turcarum), was formerly made by Prof. Agassiz 

 to include those similar and very elegant chalk species now known 

 [v.ii.] 5B 



