﻿schuchert] siluric and devonic cystidea 249 



Basal plates Eour; those of the scries above not determined. Base 

 depressed. The species have the general aspeel of Callocystites or 

 Lepadocrinus. Column unknown." 



[aekel's 1 definition of Sphcerocystites cannot be accepted, as it is 

 not based on the genotype .S'. multifasciatas, but on .V. dolomiticus 

 Jaekel (== Hemicosmites subglobosus Hall) of the Niagaran dolo- 

 mites of Chicago, Illinois. The latter species, having a greater num- 

 ber and a different arrangement of thecal plates, lias been made the 

 type of ( 'celocystis. 



Emended definition. — Callocystinse with the theca varying between 

 depressed echinus-shape with a deeply excavated base to elongate- 

 globular form with almost no excavated base. Theca with 18 plates 

 arranged as [< illows : 



Basal row has plates 4, 1,2, 3. 



Second row has plates 5. <> (sometimes part of 12), 7, 8, 9. 

 Third row has plates 10, II, 12. (7, 8), 14. 

 Fourth row has plates 16 (17 absent), 18, 13 (19 absent), 15. 

 Fifth row has deltoid 23, with madreporite and hydropore. 

 Anal area not prominent, bounded by thecal plates 7, 8, and 13. It 

 is composed of 2 circles of plates, an outer of from 10 to 14 pieces 

 of variable size, and the pyramid with 6 or 8 pieces. 



( >ne basal and 2 upper discrete-pectinirhombs, with numerous 

 dichopores. 



Ambulacra not much elevated above, and but slightly excavated 

 into, the theca, beginning with 4 rays and bifurcating variously in 

 different specimens of the same species, until 2J branchlets result. 

 Brachioles widely separated, slender, short and club-shaped. 



Madreporite large, with a small hydropore immediately below. 

 The latter is closed by a pyramid of 4 or 5 pieces. 



Column stout, tapering rapidly for a short distance and then 

 hardly at all throughout the remainder of its length. Total length 

 about 95 mm. Base of attachment terminating in a few roots. 

 Genotype, 5. rmdtifasciatus Hall. 



To the foregoing description should be added the fact that in 5". 

 multifasciatus plate 12 enters the second row and rests partly on 

 plate 6 and directly on plate 2 of the basal row. This is due to the 

 depressed form of the theca. In S. globularis the case is different, 

 as plate 12 rests directly on plate 6. 



The feature distinguishing Sphcerocystites from all the associated 

 genera is that the theca has but 18 plates. Plates 17 and 19 of other 



1 Stammesgeschichte, etc., 1, 1899, pp. 288-9. 



