SYSTEMATIC CLASSIFICATION OF WIIINI. 207 



interamhulacrul urea. Plates not imbricate, Inn ambulacra! plat.-i I. the 



interambulacra! on adradial sutures. Primordial interariiluilucrul plate* retort 

 One row only of interambulacral plates rcsorbcd in advance of the peris t. 

 Oculars usually all insert, genitals usually with tlir.-.- in five porn erli. I 

 stome with many rows of ambulacra! ami somr inierradial non-ambulacra! platen 

 (Plate 5(5, figs. 7, 8). Secondary spines and im|M-rforat<- tubrrcli-* only. 



Funiily I'M.M K insn.o 



Two columns of plates in each ambulacra! area. c..n.,i-,ting of pl.it.-, which un- 

 all primaries; pore-pairs uniserial. Four tc. si\ column^ of plate* in 



interambulacral area I'nlm-.rhimu (four species). 



Two columns of plates in each ambnlacrul an... ...noting of plates which rr 



alternately primaries and partially or completely occluded; pore-pain biscriul 

 Four to eight, or nine columns of plates in each iiitcramhulacral area. 



Mnccoya (six species). 



Four columns of plates in each ambulacra! area. ron-.i.sting of demi- ami occluded 

 plates; pore-pairs hiserial. Four to seven column-, of plati--. in eucli intcr- 



ambulacraJ area Lorrn<-rhinu* (six species). 



Four columns of plates in each ambulacra! area, consisting of demi-. ix-cluded, 

 and in addition scattered isolated plates; pore-pair-, multi^-rial l-'mir to nin<- 

 columns of plates in each interainhulacral area. . Oligoportu (five species). 



Six to twelve columns of plates in each amhularral area. coiiM-sting of demi-. 

 occluded, and one to four irregular columns of isolated plati-> in i-arli 

 half-area at the mid-zone; jxire-pairs multiseriiil. Thre<- to !.-.. ,-n mlumns of 

 plates in each interambulacral area. . . . .Miluni'rhiniu (fourteen species). 

 EE. Test elliptical, obovatc, spherical, or subspheroidal. Two to twenty columns of 

 plates in each ambulacral area. Three to thirteen columns of plates in each it 

 ambulacra! area. Plates imbricate. Primordial interambulacral plates in Iwsi- 

 coronal row. Base of corona not resorbed. Oculars usually all iiiM-rt. genitals 

 with one to many pores each. Periproct plated with many thick plates. I'eri- 

 stome witli many rows of ambulacra! plates only. Primary .-.pines with [K-rforate 

 tubercles, usually eccentric and irregularly distributed on interambulacral pl;r 

 with secondary spines and tubercles, or the latter only. . Family L>:rii>t>nii. 

 Two columns of plates in each ambulacral area. Four to eight columns of plates 

 in each interambulacral area. Plates quite thick, imbricating iiHxlera' 

 Secondary tubercles only, (icnital plates as far as known with only one pore 

 each, the only instance known in the Palaeozoic. Resembles Palaeechinus 

 excepting for the imbrication /x/W.rAi'nw.. (four 



Two columns of plates in each ambulacral area. Five columns of plates in each 

 interambulacral area. Plates imbricating strongly. Kccentric perforate 

 primary with secondary tubercles on interambulacral plat.->. Genital plates 

 with many pores 1'eritckodomus 



