1879.] NATURAL SCIENCES OF PHILADELPHIA. 323 



tnres. In the first place the species are more robust, having 

 thicker and more ponderous plates which form a more shallow 

 cup. They also differ in having generally an extra quadrangular 

 anal piece, which is inserted toward the right lower margin of the 

 other anal, and although it is often very small, and in some rare 

 cases entirely wanting, it is characteristic as a rule, while such a 

 plate never occurs in Cyathocrinus. A more constant difference 

 is observable in the brachials, which are proportionally shorter 

 and wider, particularly the first one, which often presents an almost 

 linear appearance. In Cyathocrinus the number of brachials is 

 very irregular, but in Barycrinus, without exception, it is fixed at 

 two. The best means of distiifction, however, is afforded by the 

 arms, which in Barycrinus are composed of rather short, heavy, 

 rounded pieces, with very narrow ambulacral grooves, while Cya- 

 thocrinus has rather slender arms and wide, deep furrows. The 

 arms also instead of regularly dichotomizing, so as to form equal 

 divisions, are simple in Barycrinus and give off armlets at regular 

 intervals. The* column in this genus is almost unique in its con- 

 struction, and very distinct from that of Cyathocrinus. It is not 

 only stouter and subpentagonal, but is divided longitudinally into 

 five sections, and has a large, highly organized central canal. 



Barycrinus has its closest affinities with Botryocrinus Angl., 

 with which it agrees in the general construction of the arms and 

 in the anal arrangement, but from which it is easily distinguished 

 by its massive body plates, the number and proportion of its bra- 

 chials, and by the column. 



Generic Diagnosis. General form of the calyx basin or low 

 cup-shaped ; often attaining a gigantic size ; plates massive, more 

 or less gibbous or protuberant. Surface coarsely corrugated, 

 granulated, or striated, with frequently a depression at each angle 

 between the plates. 



Underbasals five, of less than medium size, fully one-half extend- 

 ing beyond the column, their points in form of little triangles bent 

 upward. 



Basals large, three of them sometimes four hexagonal, the 

 other two heptagonal. Radials five, very unequal in size, the 

 right posterior and often the anterior one much the lowest, all of 

 them wider than high, pentagonal in outline ; articulating scar 

 facing outward, concave, occupying from one-half to fully two- 

 thirds the width of the plate. Brachials, two to each ray, wide 



