SYSTEMATIC CLASS IF I (ATI ON OF ECHINI. 



four, or five large plutes only. IVristomc with ten priinonlinl iiiiiluilarriil. alvi n-.n- 

 amhulacral plates. Lmtern erect. I'riumry tubercle, impcrforatc, or exceptionally 



perforate . Sul.or.ler .S Tl Hl>lH>ST.\. 



Ambulacral plates compound, or largely simple. Primordial ititcrumluilacral 

 plates resorbed. Base of corona resorbed. Oculars exsert or becoming i- 

 in the sequence I, V, IV, II, III. IVriproct with u permanent large suranal, 

 or more large plates, with small anal plates. Primary tubercles imjx-rforate, 

 or perforate. No spurs from pyramids supporting teeth. 



Family SM.I.MIUAK. 



Ambulacral plates compound. Primordial interatnbulacrul plates resortx-d. 

 Base of corona resorbed. Oculars becoming insert in the sequence I, V . [V, II, 

 III. Periproct with numerous small plates only. Primary tubercles imperfnrate. 

 Spurs from pyramids support the teeth dorsally. . Family PHYMOHOMATIDM 

 Ambulacral plates compound, composed of three elements each, at the mid-zone 

 every four or five ambulacra! plates are Ixnmd together and grown over by one 

 primary tubercle. Primordial interambulacral plates resorbed. Base of corona 

 resorbed. Oculars becoming insert in the sequence I, V, IV. Periproct with 

 many small plates only. Primary tubercles imperforate. Spurs from pyramids 



support the teeth dorsally Family STOMMI-NKI MIHAK. 



Ambulacral plates compound. Primordial interambulacral plates in the I 

 coronal row. Base of corona not resorbed. Oculars all cxscrt nr lx-<-oniing in-.cn 

 in the sequence V, I, IV. Periproct with four or five large plates only. Primary 

 tubercles imperforate. No spurs from pyramids supporting teeth. 



Family ARHAI HUM.. 



EE. Epiphyses wide, meeting in suture over the foramen magnum. Ambulacral 

 plates compound. Coronal plates not imbricate. Ambitus circular, or elliptical 

 through a sidewise axis. Primordial interambulacral plates resorbed. Base of 

 corona resorbed. Oculars all exsert or becoming insert in the sequence V, I or I, 

 V, IV, II, III. Periproct usually plated with many small plates (in one genus, 

 Parasalenia, with four large plates). Peristome with ten (in one species five) 

 primordial ambulacra! plates and more or fewer non-aml>ulucral plates; rarely 

 the latter are absent. Lantern erect. Primary tiilx-rdes impcrforate. 



Suborder CAM .11>1><>.\ T.I. 



Ambitus circular. Pits, or sculpturing in coronal plates dorsally. Ambulacral 

 plates at mid-zone composed of three elements each. Oculars usually all exsert . 



Family TKM \oi-i KIKIUM. 



Ambitus circular. No pits or sculpturing in coronal plates dorsally. Ambula- 

 cral plates at mid-zone composed of three elements cadi, rarely dorsally 

 of two elements. Oculars all exsert, or becoming i"*<-rt in the sequence I. \ . 

 IV II III. Family F.c IIIMDAE. 



Ambitus circular. No pits or sculpturing in the coronal plates. Ambulacral 



