Some new Upper Greensand Echinoderms. 23 



nules become less distinct. The pairs of pores are oblique, and 

 are separated by an oblique elevated ridge : it is between these 

 ridges that the granules are placed, which, by nearly uniting 

 their extremities, give the zones a zigzag ornamentation. The 

 space between the zones is occupied by two marginal rows 

 of granules, between which there are, round the wider part, 

 six much smaller rows of granules, of twice the number in 

 a row : at the extremities these are reduced to two rows. 

 The interambulacral areas are about five times the width 

 of the spaces between them. The plates are high, and only 

 four in each row. The scrobiculse are large, circular, mode- 

 rately deep, and above the base separated longitudinally by 

 interspaces of equal width. Excepting the uppermost one, 

 each is placed below the middle of the plate ; they are sur- 

 rounded by a prominent row of seventeen or eighteen gra- 

 nules, which are wide apart; each is placed on an elevated 

 oval base. The bosses are very moderately elevated and com- 

 pressed round the middle, so that in section the sides would 

 be concave ; a few of them are sometimes crenulated. The 

 tubercles are large, rather depressed spheres, which are placed 

 close on to the bosses. The perforation is small and circular. 

 The miliary granules are extremely small and dense on the 

 base ; they gradually become larger above. Oral and apical 

 openings both small. 



Loc. Cambridge and Ashwell. Coll. University ; J. Carter, 

 Esq. 



Spines occur not to be distinguished from those of 



Cidaris clavigera. 



Cidaris Bowerbankii. 



Cidaris, n. sp. (figured in Dixon, Geol. Sussex, t. 24. fig. 25). 



There are also spines of at least three or four unnamed species. 

 One is a large, compressed, club-shaped spine, obliquely placed 

 on a short neck; it is beautifully marked with longitudinal 

 striae, which are knotted into distant tubercles. Another is 

 extremely compressed and ornamented with fine longitudinal 

 ridges, which are granulated; its margins finely serrated. A 

 third is cylindrical and irregularly granulated. 



Besides these, there are spines nearly resembling those of C. 

 sceptrifera, but much smaller and with fewer ridges. Spines 

 occur nearly resembling those of C. sulcata, but more cylindrical 

 and having the ridges unserrated. Another form of spine may 

 belong to this species ; it is slender, has fewer and more elevated 

 ridges and a similar coronated summit. 



I abstain from attaching names to these spines, as the prac- 



