1881.] NATURAL SCIENCES OF PinLADELPHIA. 289 



inner divisions of the ray, which give off exclusively the branches, 

 with the double-jointed brachial extensions in the ray of M. pachi- 

 dactyhis, and the outer arms of the former with the branchlets of 

 the latter. 



Zittel takes Mariacrinus Hall to be a synonym of Ctenocrinus 

 Bronn, which we refer to Melocrinus, following Schultze. Hall's 

 M. mac7^opetaIus will be arranged under Gorymbocrinus Augelin, 

 and among the Calyptocrinidte. Its arms are yet unknown, but 

 the arrangement of its plates agrees perfectl}' with that genus. 

 Mariacrinus stoloniferus Hall is described only from fragmentary 

 columns. 



Amended Diagnosis.— Yorm of calyx obconical ; general aspect 

 and surface ornamentation similar to Glyptocrinus ; radiating 

 strife passing from plate to plate ; radials all along their median 

 line elevated into high rounded ridges, somewhat resembling 

 recumbent arms ; interradial and interaxillar3" arese large and 

 depressed. 



Basals four, small, almost of equal size, the one facing the anal 

 area largest. Primary" radials 3 X 5, nearl}- as wide as high, 

 decreasing in size upwards ; the first set joining laterally ; the 

 second enclosing the first anal and first interradial plates ; the 

 third supporting 3X10 seeondar}' radials, which are generally of 

 uniform size and vertically separated by six or more interaxillary 

 plates. The secondarj^ radials are followed hy several tertiary 

 radials, which vary in number with the age of the individual — 

 mature specimens having five and even more— all placed in a 

 direct line with the arras and somewhat resembling arm plates. 



Arras four to each ray, the inner ones branching, but rarely 

 more than once or twice, the outer arms remaining simple through- 

 out, and taking a somewhat lateral course. The inner arms are 

 placed close together, almost parallel with each other, their 

 branches given off to the outer sides of the ra\'. Both inner and 

 outer arms are composed of quadrangular single joints, with 

 straight, sometimes slightl}^ oblique sutures ; the arm-bearing 

 joints subpentagonal ; main arms and branches fringed with 

 pinnules. 



Interradial areae large, composed of a great number of plates ; 

 the first wedged in between the upper sloping sides of two first 

 radials and two second radials ; second interradial series con- 

 sisting of two plates ; each succeeding series of two or three. 



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