124 PSEUDODIADEMA 



F. Species from the Coralline Oolite. 



[a. Pores bigeminal in the upper part of the zones.] 



Pseudodiadema versipora, Phillips. PI. VII, fig. 4 a, b, c, d, e,f, g. 



Diadema versipora. Woodward MS., Morris, Catalogue of British Fossils, 1st ed., 



1843, p. 50. 



— subangulare. Agassiz, Description des Echinodermes Fossiles de la Suisse, 



pi. 17, figs. 21—25, p. 19. 



— — Wright, Annals and Magazine of Natural History, 2d series, 



vol. viii, p. 270. 

 Diplopodia subangularis. M'Coy, Annals and Magazine of Natural History, 2d series, 



vol. ii, p. 412. 

 — — Desor, Synopsis des Echinides Fossiles, p. 75. 



Diadema versipora. Woodward, Memoirs of the Geological Survey, Decade V. 



Notes on Fossil Diademas. 



Test circular, depressed ; ambulacral areas with two rows of primary tubercles, four- 

 teen in each row ; poriferous zones undulated below ; above the equator the pairs of 

 pores form a double series ; inter-ambulacral areas with primary and secondary tubercles ; 

 spines short, stout, pointed, covered with longitudinal lines. 



Dimensions. — Height, nine twentieths of an inch ; transverse diameter, one inch and a 

 quarter. 



Description. — This beautiful Diadem, which is so characteristic a fossil of the Coral 

 Rag of England, was formerly mistaken for the Cidarites subangularis, Goldfuss. On 

 comparing, however, a fine series of our urchins with a type specimen from the Coral 

 Rag of Nattheim, sent by Professor Roemer, and a fine large specimen from the White 

 Jura of Sigmaringen, kindly sent by Dr. Fraas, of Stuttgart, the difference is very evident. 

 The Swiss Diadema figured by M. Agassiz, and considered to be identical with Goldfuss's 

 species, agrees with our urchins in so many points of structure that I believe them to be 

 identical. P. versipora has from twelve to fourteen primary tubercles in the inter- 

 ambulacral areas, whereas P. subangulare has only from six to eight ; the test, more- 

 over, is higher and more circular, and there are more tubercles in each row in the ambu- 

 lacral areas. I have, therefore, restored the manuscript name first given to this species 

 by Professor Phillips, and afterwards adopted by Mr. Woodward. 



Pseudodiadema versipora has the test depressed ; in general it is circular ; sometimes, 



