﻿224 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



pectinirhombs are large with the halves adjoining, and the brachioles 

 few in number and widely separated. 



The genus is named for Doctor Otto Jaekel of the Geological 

 Institute of the Friedrich-Wilhelms University, Berlin, Germany, in 

 recognition of the great service he has rendered to paleontology by 

 his detailed description of the Thecoidea and Cystoidea, forming 

 volume 1 of his great contemplated work on the Stammesgeschichte 

 der Pelmatozoen. This work has been of the greatest aid in the 

 present studies, and in the accuracy of their results. 



JAEKELOCYSTIS HARTLEYI Schuchert 

 (Plate XXXVII, figures 4-8) 

 Jackelocystis hartleyi Schuchert, Amer. Geol., xxxn, 1903, p. 231. 

 Length of a full-grown theca 15 mm.; width and depth about 11 

 mm. For general form, shape of individual plates and their orna- 

 mentation, see the figures and diagram, figure 27. 



Ambulacra narrow, excavated into, and but slightly elevated above, 

 the theca, and in normal specimens extending to the column. Each 

 pair of ambulacra, or R I and R II, R IV and R V, converging and 



almost touching each other near 

 the column. In one individual, 

 R I is but half the normal length 

 and R II is almost aborted, hav- 

 ing but 6 brachioles. In an- 

 other individual R I is en- 



/ tirely undeveloped, while in a 



\ / third specimen R II is absent. 



- „„ . , . t t u 1 .■ In a fourth specimen R V is 



tic 27. — Analysis of Jaekelocystis r 



hartleyi Schuchert. forked, the branch developing 



on the left. In full-grown speci- 

 mens, there are about 34 brachioles to each ambulacrum, 17 on either 

 side. Brachioles stout and folded over each other medially ; length 

 unknown but apparently quite short. Ambulacral grooves narrow 

 and shallow, with very minute ambulacralia. 



Dichopores on plates 1, 12, and 14 not shown at the surface, being 

 deeply situated within small oval pits, each with a rim highly elevated 

 above the surface of these plates. Those on plates 5, 18, and 15 

 show the dichopores with the excavation deepest orally, and are here 

 delimited by a crescentic lip. About 8 folds in each rhomb. 



Hydropore conspicuous, situated on a small piece (plate 23), 

 placed above and between plates 18 and 13. Xo madreporite (lis- 



