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. inaquale, 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. Davidson'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 little 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, with two or four rows of secondary 



tubercles in the inter -ambulacra. 



Pseudodiadema placenta, Agassiz. Syn. Diadema placenta, Agassiz, Echinod. Foss- 



Suisse, tab. 17, figs. 16 — 20. 



