262 PROCEEDINGS OF THE ACADEMY OF [1881. 



nized by Meek and Worthen as second radials, to be mere acces- 

 sory pieces. These plates are exceedingly small and rudimentary 

 in this genus, sometimes almost obsolete ; but in their minuteness 

 they are clearly the analogues of the second primary radials in 

 other genera, and should be so described. 



Generic Diagnosis. — Calyx depressed, saucer-shaped, much 

 wider than high ; symmetry bilateral. Vault high, pyramidal, 

 pentagonal in outline, crowned by five wing-like lateral extensions 

 or processes, which form one of the most characteristic features 

 of this remarkable genus. Plates without surface ornamentation, 



Basals two, large, of similar form, pentagonal, the suture run- 

 ning from the anterior to the posterior side ; they form a shallow 

 cup, with a central depression for the attachment of the column. 

 Posterior side of the cup angularly excavated for the reception of 

 a rather large, lance-shaped, subtriangular anal plate, the opposite 

 side of which is similarly excavated, supporting the anterior 

 radial. First radials almost twice as wide as high, increasing 

 rppidly in width from their lower suture upward. The anterior 

 radial is heptagonal, the two adjoining radials hexagonal. The 

 two posterior first radials are of somewhat difierent form on 

 account of the triangular or quadrangular anal piece which is inter- 

 calated between them, and they are either heptagonal or hexagonal 

 according as this plate is of equal height with them or shorter. 

 The upper side of the first radials is excavated and more or less 

 concave, it supports not only the second primar}^ radials, but also 

 the two secondary ones, and, what is most remarkable, one of the 

 first series of tertiary radials; all of which plates, with 1 X 2 X 20 

 additional tertiary radials, form part of the calyx. The second 

 primary radial is placed within the concavity of the first plate ; 

 it is very minute, sometimes invisible externally, of triangular 

 form, and supporting on each sloping face a single series of bifur- 

 cating plates, which rank as secondary radials. These latter meet 

 above the apex of the small second radial, and rest by one side 

 upon the large first radials, while their two upper faces support 

 from 2 to 3 X 20 tertiary radials, or 2 X 4 to each ray. Of these 

 plates, the two outer ones of each ray rest with one side upon the 

 outer extremity of the margin of the first radials, with the outer 

 side against one of the upper sloping faces of the secondary 

 radials, the inner sides meet each other, while their upper faces 

 support a second tertiary radial. The two plates toward the 



