314 



GOMPAHATIVE ANATOMY 



CHAP. 



Sue-Class 3. Blastoidea. 



Armless Pelmatozoa, either pear-shaped, club-shaped, oviform, or spherical. 

 Body usually regularly radiate. Base monocyclic. Three basals, one small and 



Fig. -itiS.— Pentremites, from 



tlie side, without pinimles. 1, 



Fio. 265.— Codaster bilobatus, M'Coy, from tlie oral 

 side (after Etlieridge and Carpenter). 1, Hydrospire 

 Interradial = deltoid ; 2, 3, radials ; slits ; 2, lateral plates ; 3, ambulacral groove ; 4, mouth ; 

 4, basal ; 5, ambulacrum ; il, spir- 5, radial ; (3, suture between two radials ; 7, anus ; 8, inter- 



aclp. 



radial ; 0, ridge on an interradial. 



s^'?-- vl ^j^ i\'"^?r\ — *~' 



Fia. 264. — Granatocrinus Norwoodl 

 (after Etheridge and Carpenter) ; from 

 the apical side, with stem. 



Fig. 266.— Orophocrinus stelliformis (after Ethe- 

 ridge and Carpenter) ; from the oral side. 1, Lateral 

 plates ; 2, covering plates of the ambulacra ; 3, hydro- 

 spire slits ; 4, anus ; 5, ambulacral groove ; 6, points 

 of attachment of the pinnules. 



two larger. Five radials, more or less deejily cut out for the reception of the five 

 ambulacra. Five interradials lying above the five radials, and siu'rounding the 



