DIADEMAD.E. 85 



C. Tubercles not perforated and crenulated. 



a. Ambulacral and inter-ambulacral plates without angular impressions. 



X. Form depressed, tubercles rather large, peristome widely open . . Cypiiosoma. 



XX. Form inflated, tubercles small, peristome narrow . . • Micropsis. 



h. Ambulacral and inter-ambulacral plates marked with angular, and 

 sutural impressions. 



X. Apical disc sub-circular, inter-ambulacral tubercles forming many rows 



towards the ambitus ..... Temnopleuiius. 



XX. Apical disc pentagonal, inter-ambulacral tubercles forming two rows . Echinocyphus. 



D. Tubercles not perforated and not crenulated, 



a. Ambulacral and inter-ambulacral plates without angular and sutural 

 impressions. 



X. Apical disc smooth, ovarial and ocular plates perforated below at their ex- 

 ternal angle ...... Goniopygus. 



XX. Apical disc furnished with a large tubercle on each ovarial plate ; ovarial 



and ocular plates perforated at some distance from the border . Acropeltis. 



XXX. Apical disc granular, deprived of tubercles ; ovarial and ocular plates per- 

 forated at some distance from the border. 



X. Tubercles rather large, forming regular vertical rows. 



y. Two rows only of inter-ambulacral tubercles ; mammelon large and pro- 

 minent ...... Leiosoma. 



yy. More than two rows of inter-ambulacral tubercles ; mammelon small . Eciiixociuakis, 



yyy. Inter-ambulacral tubercles not extending above the ambitus ; inter- 

 ambulacral area forming, at the upper part, a depressed zone, 

 perfectly circumscribed. 



z. Four rows of inter-ambulacral tubercles towards the ambitus . CcelopleuPvUS. 



zz. Two rows of inter-ambulacral tubercles towards the ambitus ; spir.es 



long, sub-tricarinated, and slightly bent . . . K.eraiapiioiius. 



yyyy. Ambulacral and inter-ambulacral tubercles limited to the inferior sur- 

 face, replaced above the ambitus by caducous granules . . Codiopsis. 

 XX. Tubercles small, forming very regular horizontal rows. 

 y. Peristome small, pores simple towards the ambitus . . Cottaldia. 



yy. Peristome very wide, sub-pentagonal, pores forming double rows from 



the ambitus to the mouth .... Magnosia. 



