Dr. T. Wright on the Cidaridse of the Oolites. 249 



are sculptured with from ] 8-20 crenulations, and the areolae are 

 separated from each other by a circle of granules made more 

 prominent, inasmuch as they are raised on oval elevations of the 

 test. The principal tubercles are small and closely set together 

 at the base, but at the equator, and always at the upper part of 

 the test, they become largely developed; the narrow central 

 space between the ranges of the large tubercles is occupied with 

 an abundant granulation, the granules of which are smaller, 

 however, than those encircling the areolae. 



The mouth is armed with powerful jaws and teeth, which are 

 not, however, preserved in the specimens before me; the apical 

 disc is unknown. 



The spines attain a great size ; they have an elongated thick 

 subcylindrical form which suddenly expands above the neck, and 

 then gradually tapers towards the apex ; their surface is covered 

 with small granulations, very uniform in size and disposed in lon- 

 gitudinal rows ; the tubercles of the adjoining rows alternate, and 

 each series is connected by a filament which passes from one 

 tubercle to another ; at the summit of the spine the granules 

 become elongated, and expand to form a radiated star-like disc ; 

 the neck of the spine is short and smooth, the articulating head 

 is small, and the rim of the acetabulum is encircled with crenu- 

 lations. 



Affinities and differences. — C. Blumenbachii is distinguished 

 from C. Fowleri in the extreme narrowness of the ambulacral areae, 

 the size and prominence of the granules which cover the same, 

 and in the closer approximation of the pairs of pores in the avenues. 

 The interambulacral areae are wider, whilst the central granular 

 space between the tubercles is narrower ; there are fewer ranges 

 of tubercles in the areae, and the areolae are encircled by much 

 larger granules ; but it is in the structure of the spines that the 

 greatest difference is observed : instead of the well-known regular 

 form of the tubercles so constant in the spines of C. Blumenbachii, 

 the spines of C. Fowleri are compressed and covered with irregular 

 rows of prickles. 



Locality and stratigraphical range. — This Urchin is very cha- 

 racteristic of the Coralline Oolites of Wilts, Oxfordshire, and 

 Yorkshire ; we have never seen it either in the Inferior or the 

 Great Oolite ; our specimens are from the Coral Rag of Wiltshire ; 

 it occurs in France in the corallian stages of Chatel-Censoir and 

 Druyes and in the environs of Tonnerre, and at Bailly and at 

 Courson *. In Germany it was found at Thurnau and Muggen- 

 dorf f ; in the coralline Oolite of Hildesheim in the kingdom of 

 Hanover % ; in Switzerland in the terrain h chailles of Fringelli, 



* Cotteau, Echin. Foss. p. 110. f Goldfuss, Pctr. Germanise, p. 117. 

 X A. Roemer, Norddeutsches Oolithen Gebirge. 



