140 FOREIGN OOLITIC PSEUDODIADEMAS. 



tubercles, which at the base, and up to the equator, nearly equal in size the two rows of 

 primary tubercles ; this imparts a tetragrammous appearance to this species, which is lost, 

 however, in the upper part of the area, where there are only two rows of tubercles ; 

 ambulacra moderately wide, their tubercles nearly as large as those of the inter- 

 ambulacra ; pores unigeminal throughout ; apical disc small and ring-like, all the plates 

 covered with a fine granulation ; rows of small granules separate the areolas from each 

 other ; mouth opening large ; peristome not deeply notched. 



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

 one twentieth of an inch. 



Formation. — Corallien de Bensan^on, de Chatel-Censoir (Yonne). 



Collections. — Museum of Vienna (Collection Dudressier), Coll. M. Cotteau. Very 

 rare. 



PsEUDODiADEMA iEQUALE, Agassiz. Syn. Diadema csquale, Agass., Echinod. Eoss. 



Suisse, part ii, tab. 17, figs. 36 — 38. 



Test circular hemispherical, depressed above ; ambulacral rather smaller than the 

 inter-ambulacral tubercles; areolas confluent; four rows of small secondary tubercles, 

 which only extend to the equator ; upper part of the miliary zone naked ; mouth opening 

 moderately large ; peristome not deeply notched ; pores strictly unigeminal, falhng into 

 triple oblique pairs near the mouth. This species very much resembles P. hemispharicum, 

 but the smallness of the secondary tubercles, the shortness of the rows, and the nakedness 

 of the upper part of the miUary zone, distinguish it from that allied form. 



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

 and two fifths. 



Formation. — Argovien des environs d'Arau. Kellovien des environs de Quingey. 



Collections. — Museum Bale, Coll. Zschokke, Marcou. Very rare. 



PsETJDODiADEMA AFEiNE, Agassiz. Syn. Diadema affine, Agass., Echinod. Eoss. Suisse, 



part ii, tab. 17, figs. 54 — 58. 



Test small, circular, depressed; the secondary tubercles at the zonal sides of the 



