234 ACROSALENIA. 



Affinities and differences. — This species resembles Acrosalenia hemicidaroides, Wright, 

 but is distinguished from it by having the test more depressed, the ambulacral tubercles larger 

 and more prominent, the three upper pairs of the primary inter-ambulacral tubercles smaller, 

 with a naked median depression in the centre of the upper part of the miliary zone ; the 

 apical disc is likewise smaller. The size and prominence of the ambulacral tubercles form 

 a distinctive character between Acrosalenia Lycettii and Acrosalenia pustulata on the 

 one side, and Acrosalenia Wiltonii on the other, both of which have small and widely 

 spaced-out tubercles in the ambulacral areas. 



Locality and iSlratiyraphical position. — I have collected this urchin from the 

 lower ferruginous beds of the Inferior Oolite, the Pea grit, at Crickley, Leckhampton, 

 and Cooper's Hills; from a sandy seam of the lower beds of the Inferior Oolite at 

 Stinchcombe ; and likewise from the lower beds of the Inferior Oolite at Brockhampton, 

 Cleeve, and Sudely Hills. It occurs likewise in the shelly beds of the Roe-stone at 

 Leckhampton, and has been catalogued in the Rev. P. B. Brodie's paper* as Acrosalenia 

 Hoffmani, Romer. Although an abundant species, it is seldom found in good preservation, 

 the shell being always more or less crushed ; it is commonly associated with Pseudodiadema 

 depression, Agass., which it somewhat resembles, but is easily distinguished from that 

 form by the disproportion between the size of the ambulacral and inter-ambulacral 

 tubercles. 



History. — It was first figured and described in my ' Memoir on the Cidaridae of the 

 Oolites/ and is dedicated to my friend John Lycett, Esq., one of the learned authors of the 

 ' Monograph on the Mollusca of the Great Oolite, 3 which has already enriched the volumes 

 of the Palaeontographical Society. 



C. Species from the Great Oolite, Bradford Clay, Forest Marble, and Cornbrash. — 



ll e JEtaye Bathonien, D'Orbigny. 



Acrosalenia hemicidaroides, Wright. PI. XV, fig. 4 a, b, c, d, e,fg, h, I, m. 



Acrosalenia hemicidaroides. Wright, Annals and Magazine of Natural History, 2d ser., 



vol. viii, p. 161, pi. 11, fig. 1. 



— — Forbes, Memoirs of the Geological Survey, Decade IV, 



pi. 2. 



— — Forbes, in Morris's Catalogue of British Fossils, 2d edit., 



p. 70. 



— — Desor, Synopsis des Echinides Fossiles, p. 144. 



* 'Quarterly Journal of the Geological Society,' vol. vi, p. 247. 



