1) \\ KNPOKr ACADF.MY OK NATURAL SCIKNCKS. 



STEREOCRINUS Barris. {Kciised.) 



BY W. H. BARRIS. 



1S7S. Proc. D;iv. Ac:id. Nat. Sci.. \'ol. II., p. 2S3. 



iSSi. Revision of llic Pulxocrinoidea by Messrs. Waclisiuutli and Sprintjcr, Part II., p. 126, 

 where it is classified as a sub-gentis of Dolatocrinus Lyon. 



The most apparent distinction between Dolatocrunis and Stereocri- 

 niis is the existence in the former of three radial plates to the ray, 

 while in the latter there are but two. 



Body variable in form and size ; calyx either broad, shallow, or 

 basin-shaped, the bottom comprising the basal disc, together with the 

 first radials, the greater part of the second radials and first interradials, 

 in the same horizontal plane; sides short, abrupt; dome low; or the 

 greater part of the second radials, and the whole of the first interra- 

 dials, rise into and form the sides of the calyx, which curve gradually; 

 dome low, yet increasing somewhat in height with the height of the 

 calyx. Interradial portions depressed, deepening toward the arm- 

 bases, thus giving the radial portions of the vault a prominent position, 

 enhanced, in this genus, by cons])icuously projecting arm-bases. Ven- 

 tral aspect pentalobate. Basals three, small, nearly equal, closely 

 anchylosed, forming a shallow, funnel-shajjed disc, which is pentag- 

 onal, and scarcely extends beyond the column. 



Primary radials 2x"), the first hexagonal, the second pentagonal, 

 supporting on each of its upper sloping sides two radials of the second 

 order, the upper one serving as a brachial plate. This gives two arms 

 to the ray, making ten in all. These bifurcate, and are composed of 

 a double series of small joints, interlocking with each other. 



Interradials two, large, with several smaller ones above, the two 

 forming in series of one each. The first is most generally the largest 

 ])late in the body, heptagonal, resting between the two upper sloping 

 lateral sides of the two adjacent first radials, having on either side, 

 above these, the second radial and the first secondary radial. It sup- 

 ])orts on its ui)per truncated side the second large interradial, which is 

 hexagonal, and almost of the size of the second radials. The succeed- 

 ing order of interradials is generally composed of three small irregular 

 plates, reaching up into the depression of the dome, and actually form- 

 ing ])art of it. .Vnal series undistinguishable from the interradial series. 



