FOREIGN OOLITIC PSEUDODIADEMAS. 137 



other parts those of each area very much resemble one another ; there are fewer tubercles 

 in a row in the ambulacra than in the inter-ambulacra; the poriferous zones are narrow, 

 and the pores are unigeminal on the upper surface ; the mouth opening is small, and the 

 decagonal peristome is divided into nearly equal-sized lobes ; there are no secondary 

 tubercles at the base of the inter-ambulacra. 



Dimensions. — Height, three twentieths of an inch ; transverse diameter, two fifths of 

 an inch. 



Formation. — " Portlandien inferieure (Astartien) de Rsedersdorf (Haut Rhin), du 

 Jura Neuchatelois, des bords du Doubs, de Laufon. 



Collections. — MM. Gresly, Thurmann. Desor. Rare." 



PsEUDODiADEMA IN^,QUALE, Agassiz. Syu. Biadema incsquale, Agassiz, Cat. syst., p. 8. 



Test small, subpentagonal, and depressed ; tubercles small, uniform, and numerous ; 

 inter-ambulacral tubercles arranged near the poriferous zones ; miliary zone wide, and 

 naked from the equator to the apical disc ; mouth opening of moderate size ; peristome 

 divided into equal-sized lobes ; opening for the disc large, and oblong ; the approximation 

 of the tubercles into groups of four rows, separated by the wide naked miliary zone in the 

 upper part of the areas, serves to distinguish this species from aUied forms. It differs 

 from P. superhum in having the tubercles set closer together, and from P. textum in 

 having wider ambulacral areas. 



Dimensions. — Height, two fifths of an inch ; transverse diameter, four fifths of an 

 inch. 



Formation. — Kellovien de Marolles, de Chaufour, et Montbizot (Sarthe), Lifol 

 (Vosges). Common. 



Collections. — MM. Michelin, d'Archiac, d'Orbigny. The specimens in my Cabinet 

 were kindly sent me by M. Triger, of Le Mans. 



PsEUDODiADEMA supERBUM, Agassiz. Syu. Biadema superhum, Agass., Echinod. Foss. 



de la Suisse, tab. 17, fig. 6 — 10, p. 23, 

 part ii. 

 Test small, subpentagonal, and sometimes inflated at the sides ; ambulacral tubercles 



18 



