Dr. T. Wright m fifc Cidaridae <>f th, Oolites. 157 



timet the width of tin- ambulacra!, and poaacM i double range of 

 primary tubercles from seven to eight in each range. The mam- 

 miliary eminences supporting them are very prominent, and arc 

 surrounded by an elliptical areola. The summits of the mammae 

 are sculptured with about ten crenulations. The tubercles are 

 disproportionately small when compared with the development 

 of the mammae supporting them ; the two ranges of tubercles 

 are separated by tour rows of granulations which form zigzag 

 granular bands descending down the centre of the areae ; similar 

 binds ol granulations bound the external borders of the inter- 

 ambulacra, and separate the ranges of the principal tubercles 

 from the poriferous avenues; the upper and lower borders of the 

 areolae are confluent, but the other parts of their circumference 

 are surrounded by a wreath of granules. The mammillary emi- 

 nences and tubercles are largest at the equator, gradually dimi- 

 nishing as they approach the oral and anal poles. The pores are 

 large and disposed obliquely in simple pairs. The mouth -open- 

 ing is large and decagonal, the marginal notches being of mo- 

 derate depth. The apical disc is absent in all the specimens we 

 have found ; it is therefore impossible to state whether the anal 

 opening was situated before or behind the single madreporiform 

 plate. 



Affinities and differences. — This species is distinguished from 

 A. hemicidaroides in having the areolae more excavated and ellip- 

 tical. The granules occupying the intertubercular spaces are 

 smaller and more numerous. The tubercles of the interam- 

 bulacra are disproportionately small when compared with the 

 development of their mammae ; the circumference has in general 

 a subpentagonal outline, from the prominence of the ambulacral 

 area*, the double row of tubercles on which is more fully deve- 

 loped than in A. hemicidaroides. These differences between the 

 tests of our two species although inconsiderable are nevertheless 

 connected with others, which although not seen may be inferred, 

 as t he differences in the size and form of the primary and secondary 

 spines belonging to the tubercles of both areae leave no doubt 

 on our mind that A, Lycetti is distinct from A. hemicidaroides, 

 and we know of no other species among its congeners for which 

 it could be mistaken. A granulated spine, and of which we give a 

 figure (2 d) y found frequently in the same beds with A. Lycetti, 

 and probably belonging to this species, it' proved to be such, 

 would form an important specific character. 



Lociil'itij and stnitit/niphical range. — We collected this Urchin 

 from the lower t'eiru-mous beds. Tea-grit, of Crickley Hill, and 

 have found it in the same stratum at Leckhampton, Cleeve, and 

 Broekhampton quarries. The specimens are in genera] • 

 (rushed, and the apical disc is always 



