FROM THE INFERIOR OOLITE. 197 



Polycyphus Normannus, Desor. PL XIII, fig. 4 a, b, c, d, e,f. 



Polycyphus nodulosus. Agassiz and Desor, Catalogue raisonnedes Echinides, Annales des 



Sciences Naturelles, 3 me serie, tome vi, p. 361, pi. 15, fig. 18. 

 Arbacia nodulosa. Wright, Annals and Magazine of Natural History, 2d series, 



vol. viii, p. 279, pi. 13, fig. 3 a, b. 

 Polycyphus nodulosus. Wright, Annals and Magazine of Natural History, 2d series, 



vol. xiii, p. 1/8. 

 Echinus nodulosus. Morris, Catalogue of British Fossils, 2d edit., p. 79. 



— — Salter, Memoirs of the Geological Survey, Decade V, pi. 4, p. 8. 



Polycyphus Normannus. Desor, Synopsis des Echinides Fossiles, p. 117, tabl. 19, 



figs. 4 — 6. 



Test circular, hemispherical above, flattened at the base ; ambulacral areas a little more 

 prominent than the inter-ambulacral, with six rows of tubercles at the equator; inter- 

 ambulacra with fourteen rows of tubercles disposed in vertical and transverse lines ; 

 tubercles of both areas smooth, round, and nearly of the same size ; basal tubercles much 

 larger ; poriferous zones wide, pores in trigeminal ranks ; inter-ambulacra divided by slight 

 median depressions, and naked at the upper part of the centro-suture : apical disc small 

 and ring-like ; base flat ; mouth opening large ; peristome very unequally lobed. 



Dimensions. — Height, seven twentieths of an inch ; transverse diameter, eleven 

 twentieths of an inch. 



Description. — This pretty little urchin has been long confounded with Magnotia 

 nodulosa, Miinster, from the Coral Rag of Nattheim, which it resembles much in its 

 general physiognomy, but is distinguished by the structure of its ambulacra and poriferous 

 zones, the pores in M. nodulosa being unigeminal, whilst in P. Normannus they are 

 trigeminal : for this reason M. Desor has properly described it as a distinct species. Its 

 hemispherical test exhibits a disposition to assume a sub-pentagonal form, in consequence of 

 the prominence of the ambulacral areas (fig. 4 a, b) ; the surface of the test is divided into 

 fifteen nearly equal lobes by the ten wide poriferous zones, and a median depression in the 

 centre of the inter-ambulacra (fig. 4 e) ; these lobular divisions are more marked in young 

 and small specimens than in old and large ones ; the ambulacral areas (fig. 4 b, e) are one half 

 the width of the inter-ambulacral, they have nine large tubercles at their base (fig. 4, e,f), 

 and six rows of small tubercles at their widest part (fig. 4 e), which gradually diminish to 

 four and two rows above (fig. 4 b). 



The inter-ambulacral areas are twice the width of the ambulacral (fig. 4 b), and are each 

 divided by a median depression into two equal-sized lobes (fig. 4 c) ; they have from 

 twenty to twenty-four large tubercles at their base (fig. 4 c), and from twelve to fourteen 

 tubercles on the same line at their widest part (fig. 4 e), which gradually diminish by the 

 disappearance of the lateral rows to ten, eight, six, four, and two (fig. 4 b) ; the row on 



