1886.] NATURAL SCIENCES OF PHILADELrHIA. Ill 



radial, which toward the left supports a series of anal plates; 

 toward the right the brachials. Arms long ; the pinnules some- 

 times take the form of arms, and attain the same general height. 

 Column tri- or quinque-partite. 



G. Anomalocrinid^. Base monocyclic. Form irregular. Calyx 

 cajjacious. Azygous plate large ; supporting the right posterior 

 radial, which toward the right is succeeded by a row of brachials, 

 and toward the left by the ventral tube. Arms composed of large 

 quadrangular joints, giving off pinnules from one side only, from 

 one bifurcation to the next, when all pinnules change to the oppo- 

 site side. Column strong, central canal wide, stelliform, its pro- 

 jecting angles directed inter radially. 



D. Belemnocrinid^. Base monocyclic. Basals large ; cylin- 

 drical ; solid, only pierced b}^ a narrow central canal with a shal- 

 low concavity at its npper end, Eadials small, quadrangular, 

 enclosing an anal plate of the same form. Ventral sac large, 

 club-shaped. Arms long with numerous sj'zygies, only every 

 second or third joint pinnule-bearing. Pinnules long, often 

 bifurcating. Column round or pentangular, frequently with long 

 cirrhi given off interradially. 



E. CYATHOCRiNiDiE. Base dicyclic. Calyx globose, rarely 

 turbinate. Radials with horseshoe-like lateral facets supporting 

 at least two, but frequently several more brachials. Arms without 

 true pinnules, but with branches in regular succession to their 

 tips. Arm joints with a few exceptions long and narrow ; quad- 

 rangular with almost parallel sides ; united either by suture or 

 ligament, apparentl}^ not by muscles. Ventral sac large, C3din- 

 drical. Column round or pentagonal ; central canal rather above 

 medium size, pentagonal, the projections directed radially. 



F. P0TER10CRINID.E. Base dicj^clic. Calyx deep and turbi- 

 nate, or shallow and disk-like, owing to the form of the under- 

 basals, which are either extended into a cup, or are turned inward 

 and concave. Radials somewhat irregular, of variable size, the 

 right posterior one generally smaller ; all truncated at the upper 

 face. Brachials one or two, connected by suture ; the lower or 

 l)roximal face truncate. Arms simple or branching, with pinnules 

 alternately arranged from every joint ; without syz^^gy. Arm 

 joints cuneate or interlocking. Articulation between brachials 

 and radials by muscles and ligament, and also between the upper 



