264 Dr. T. Wright on the Cidaridse of the Oolites. 



branches which inclose the areolae of the tubercles for about two- 

 thirds of their circumference, leaving the areolae open to the 

 poriferous avenues. The interambulacral arese are nearly three 

 times the width of the ambulacral, and possess a double range of 

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

 millary eminences supporting them are very prominent, and are 

 surrounded by an elliptical areola. The summits of the mammse 

 are sculptured with about ten crenulations. The tubercles are 

 disproportionately small when compared with the development 

 of the mammse supporting them ; the two ranges of tubercles 

 are separated by four rows of granulations which form zigzag 

 granular bands descending down the centre of the arese ; similar 

 bands of 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 mamraillary emi- 

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

 nishing as they appi'oach 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 ambulacra! 

 arese, 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 the differences in the size and form of the primaiy 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), found frequently in the same beds with A. Lycetti, 

 and probably belonging to this species, if proved to be such, 

 would form an important specific character. 



Locality and stratigraphical range. — We collected this Urchin 

 from the lower ferruginous beds, Pea-grit, of Crickley Hill, and 

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



