256 FOREIGN OOLITIC ACROSALENIAS. 



Formation. — The White Jura e of Nattheira = Coral Rag. 

 Collection. — Museum of Tubingen. 



Acrosalenia Kcenigii, Desmoulins. Syn. Diadema Koznigii, Desmoulins. Etudes sur 



les Echinides, Tabl. Synod., p. 312, No. 10. 



Hemicidaris Konigii, Agassiz. Catalog, 

 raisonne des Echinides, Annal. Sc. Natu- 

 relles, 3 me serie, tome vi, p. 337. 



Hemicidaris Boloniensis, Cotteau, in Desor's 

 Synopsis des Echinides Fossiles, p. 53. 



Test hemispherical, base flat, sides inflated ; ambulacra narrow, straight, with two 

 rows of small, marginal tubercles, and a double row of granules within ; inter-ambulacra 

 more than three times as wide as the ambulacra, with two rows of large primary tubercles, 

 eight to nine in each row ; the bosses of the tubercles large, with wide, oval areolas ; miliary 

 zone composed of two or three rows of granules ; apical disc small, the right anterior 

 genital plate supports a large, prominent, spongy madreporiform body ; single genital 

 plate small and crescentic ; sur-anal compound, number of pieces unknown ; mouth 

 opening large ; peristome unequally decagonal ; primary spines long, cylindrical, and 

 tapering. 



The discovery of a portion of the sur-anal plate, in situ, added to the excentral position 

 of the vent, and the absence of semi-tubercles from the base of the ambulacra, are my 

 reasons for removing this urchin from the genus Hemicidaris, and placing it in Acrosalenia. 

 1 have, at the same time, retained M. Desmoulin's specific name. 



Dimensions. — Height, one inch (?) ; transverse diameter, one inch and three quarters. 

 Mr. Davidson's specimen exceeds these dimensions. 



Formation. — Etage Kimmeridgien, Ningles, near Boulogne-sur-Mer. 



Collections. — British Museum, MM. Michelin, Desmoulins, Cotteau, Bouchard- 

 Chantereaux, Davidson, my cabinet. The two largest specimens I 

 possess were collected, and kindly given me, by M. Bouchard. The 

 species is rare, these two specimens being all that eminent palaeon- 

 tologist collected in thirty years. Mr. Davidson has figured, in his 

 original manuscript plates, a very beautiful specimen contained in his 

 collection, which has the spines in situ. 



