QENERA AND GROUPS OS THR ECHINOIDEA. 09 



areas. Every compound plate has not a tubercle, for smaller 

 wedge-shaped compound plates intervene between those with 

 tubercles. 



Interradia with sunken median areas ; plates distinctly sutured 

 and high. Primary tubercles of both areas well developed, some 

 on raised areolae, all with a broad-based conical boss, largely cre- 

 nulated, with ridges passing down their tall flanks, and a small 

 imperforate mamelon. Secondary tubercles and granules sharply 

 pointed and spiny. 



The apical system and peristome of the species of this inter- 

 esting group are lost. 



Fossil. Eocene : Asia, W. Sind. 



The place of tbis genus must be provisionally with the Dia- 

 dematidse. 



Genus Phtmechhstus, Desor, 1858, Synopsis, p. 133, pi. xvii. his. 



Test rather large, tumid in marginal outline, subhemisphe- 

 rical, and depressed abactinally, broad, flat, and slightly tumid 

 actinally. Coronal plates numerous. 



Apical system small ; madreporite large ; basals unequal, some 

 radial plates entering the periproctal ring. 



Ambulacra straight, rather broad, especially actinally ; pairs of 

 pores diplopodous, close vertically, crowded at the peristome ; 

 plates compound, with at least five pairs of pores. Interpori- 

 ferous areas with two vertical rows of large, projecting, plain, 

 imperforate primary tubercles, with many surrounding granules, 

 extending from the peristome to the apex. 



Interradia broad, with two very prominent vertical rows of 

 primary tubercles, resembling in structure those of the am- 

 bulacra, but larger, with four rows of small secondary tubercles, 

 extending nearly to the peristome and diminishing above the 

 ambitus. 



Peristome very large, decagonal, with very decided branchial 

 incisions ; interradial lips small. 



Fossil. Oolite : Europe. 



Grenus Asteropsis, Cotteau, 1883, JBidl. Sac. Zool. de France, 

 ser. 2, vol. viii. p. 450. 



Test of m.odcrate size, circular in ambital outline, swollen 



