﻿schuchert] siluric and devonic cystidea 243 



One basal and 2 upper generally discrete and rarely closely adjoin- 

 ing pectinirhombs, each discrete-rhomb being generally completely 

 bounded by a highly elevated thickened margin. 



Ambulacra wide and prominent, consisting of 5 simple ones or one 

 or all of the rays may divide once, so thai there maj be from 5 to 

 10 ambulacra near the base of the theca. Brachioles widel) sepa 

 rated, slender, and very long. 



( lenotype, ( '. jewettii I [all. 



Jaekel gives _'4 plates in his diagram of Callocystites, but it is cer- 

 tain that 25 arc present. Bather, basing his diagram on Hall's work, 

 also gives -25. The difference lies in the fact that plates 24 and half 

 of 23, which are separate in the present specimens, are united by 

 Jaekel. 



The irregular variation in the branching of the ambulacra led the 

 latter author to state that it " gives one the impression of a degenera- 

 tion process." To the present writer it appears just the opposite, for 

 if Callocystites is descended from a form having throughout life 5 

 simple rays, then the bifurcation of the rays beginning in Callocystites 

 and developing to an extreme in Sphcerocystites (apparently a de- 

 scendant of the former) shows the course of development to be a 

 progressive one. The degree of arm bifurcation in Callocystites is 

 evidently not of specific value, and only occasionally is the primitive 

 character of 5 simple rays maintained throughout growth in C. 

 jewettii. It is to the latter type, illustrated by Hall in 1852, that 

 Haeckel restricted the present genus, the specimens with bifurcated 

 ambulacra being placed by him in a distinct genus under the name 

 Anthocystis. In the opinion of the writer, Haeckel's generic dis- 

 tinction has not even the justification of a variety. 



Callocystites is an American genus, of which only two species, C 

 jewettii and C. canadensis, are known. 



CALLOCYSTITES JEWETTII Hall 

 (Plate XXXIV, figures i, 2) 

 Callocystites jewettii Hall, Nat. Hist. New York, Pal., 11, 1852, p. 239, 

 pi. 50, figs. 1-18. — Jaekel, Stammesgeschichte der Pelmatozoen, 1, 

 Thecoidea und Cystoidea, 1899, p. 290, text-fig. 64 on p. 291, pi. 15, 

 figs. i-ic. — Grabau, Bull. N. Y. State Mus., ix, 1901, p. 151, text-fig. 

 47. — Grabau, Bull. Buffalo Soc. Nat. Sci., vn, 1901, p. 151, text-fig. 



47- 



Callocystis jewetti Zittel, Plandbuch der Pakeontologie, 1, 1879, p. 410, 

 text-fig. 290; p. 421, text-fig. 297. — Haeckel, Amphorideen und Cys- 

 toideen, etc., 1896, p. 131, pi. 3, figs. 21, 22. — Bather, Treatise mi 

 Zoology, in, Echinoderma, 1900. p. 62, text-fig. 31. 



Anthocystis halliana Haeckel, Amphorideen und Cystoideen, etc., 1896, 

 p. 132, pi. 3, figs. 23, 24. 



