138 FOREIGN OOLITIC PSEUDODIADEMAS. 



smaller than the inter- ambulacral, diminishing rapidly in size on the upper part of the 

 areas ; inter-ambulacra with two rows of primary tubercles, but no secondary ones ; 

 areolas surrounded by complete circles of small granules ; miliary zone wide, with fine 

 granulations at the equator, but naked at the upper part ; mouth-opening small, situated 

 in a concavity; discal opening large and oblong. This species very much resembles 

 P. ineBquale, and it may be only a small variety of that Kellovian form. 



Dimensions. — Height, one quarter of an inch ; transverse diameter, half an inch. 



Formation. — Oxfordien marnes, des Vaches-noires, Calvados ; de Mont Vohayes, Jura 

 Bernois, de Belfort. 



Collections. — Museum Paris, Coll. MM. Gresly, Michelin, my Cabinet. 



PsEUDODiADEMA MAGNAGRAMMA, Wright, nov. sp. Davidsou's MSS., pi. 3 bis, figs. 4 — 6. 



Test circular depressed, with two rows of tubercles in the inter-ambulacra ; ambulacra 

 two thirds the width of the inter-ambulacra ; tubercles of both areas set on bosses, with 

 a very large base ; those of the ambulacra are a Httle smaller than those of the inter- 

 ambulacra ; the ranges of tubercles in both areas are separated by a single row of small 

 granules ; the discal opening is small, and the mouth opening is concealed ; there are 

 no secondary tubercles, and the pores are strictly unigeminal. 



Dimensions. — Height, nine twentieths of an inch ; transverse diameter one inch and 

 one twentieth of an inch. 



Formation. — Collected from the Portland beds, between Portel and Equihen, 

 Boulonnais. 



Collections. — Mr. Davidson, M. Bouchard Chantereaux, my Cabinet. 



B. Pores unigeminal in the upper part of the zones, toith tivo or four rows of secondary 



tubercles in the inter -ambulacra. 



PsEUDoniADEMA PLACENTA, Agassiz. Syn. Diadema placenta, Agassiz, Echinod. Foss- 



Suisse, tab. 17, figs. IG — 20. 



