GENEEA AND GROUPS OF THE ECHINOIDEA. 205 



VII. 



The Suborder Spatangoidea and Families. Family Ananchytidse and Genera, 

 its Subfiimily Urechininje and Genera. Family Spatangidse and its divisions, 

 the Adetes and Genera ; the Prymnadetes and Genera ; the Prymnodesmia and 

 Genera ; the Apetala and Genera. Family Leskiidse and Genus. Family 

 Pourtalesiidse and Genera. 



II. Suborder Spatangoidea. 



Esocjclic nodostomes, with tlie peristome excentric in front, 

 rarely pentagonal in the adult, usually with a posterior lahrum, 

 behind which is a long phistron, either with a meridosternum 

 or an amphisternutn, bounded laterally by the posterior am- 

 bulacra. Periproct posterior, and either iuframarginal, supra- 

 marginal, or marginal. Apical system with four perforated basal 

 plates, compact, or the madreporite may vary in its extension, or 

 elongate. Ambulacra dissimilar. Tentacles heteropodous, either 

 simple, branchial, or penicillate or disciferous. Interradia with 

 a single peristomial plate ; the postero-lateral areas usually un- 

 symmetrical actinally. Spheridia numerous. Fascioles present 

 or absent. 



I. Family Ananchytid^. 



II. „ SPATANGlDiE. 



III. „ LESKIID.E. 



IV. ,, POURTALESIIU^. 



I. Family Anakchttid^. 



Testa ovoid or subcordiform in marginal outline, tall or de- 

 pressed ; with or without an anterior groove ; plates large. 

 Apical system elongate or semi-disjunct ; the madreporite in 

 the right anterior basal plate, rarely diffused. 



Ambulacra in a bivium and trivium, similar or slightly diverse, 

 flush, apetalous ; pairs of pores largest near the apex and at the 

 peristome, may be uniporous. 



Interradia all entering the peristome with a single plate, the 

 postero-lateral unsyrametrical actinally, the posterior with a 

 labrum and a long many-plated meridosteriium, tuberculate and 

 bounded by broad ambulacra. 



Periproct either posterior, marginal, inframarginal, or supra- 

 marginal. 



Ornamentation small. Tentacles heteropodou?. A marginal 

 fasciole may exist. 



