﻿schuchert] siluric \m> devonic cystidea 245 



unknown but exceeding 6 cm. The upper half is composed of about 

 22 stout, highly carinated segments, die lov, er 1 mes having the periph- 

 ery more and more crenated. The lower half of the column is 

 composed of high and slender, longitudinally striate segments. 



The form with divided ambulacra, which I lall described and illus- 

 trated as the typical form of ( '. jewettii, was taken by Haeckel as the 

 genotype for his genus Anthocystis, and named . /. halliana. Jaekel 

 considers the form with 5 unbranched ambulacra as possibly worthy 

 of specific distinction, but with justice adds " in no ease can one make 

 it, as Haeckel lias done, displace the type of CaMocystites." In the 

 present instance it is not regarded as worthy even of a varietal name. 



Formation and locality. — When the Erie canal was dug. Colonel 

 Jewett obtained quite a number of specimens in the Rochester shales 

 about Lockport, New York, but the species is now a very rare one. 

 In recent years Mr. J. Pettit found a number of excellent examples 

 at Grimsby, Ontario, in the same geological horizon. These are 

 now in the collection of Dr. B. E. Walker, Toronto, Canada, and 

 were kindly lent to the writer for study. 



Cat. number 35,136, U. S. N. M. Presented by Dr. Walker. 



CALLOCYSTITES CANADENSIS (Billings) 



(Plate XXXIV, figure 3) 



Apiocystitcs canadensis Billings, Geol. Surv. Canada, Cat. Sil. Foss. An- 



ticosti, 1866, p. 90. 

 Callocystites tripectinatus Ringueberg, Bull. Buffalo Soc. Nat. Sci., v, 



1S86, p. 12, pi. 1, fig. 10. 



This species is distinguished by the fact that the 2 halves of each 

 pectinirhomb closely adjoin, there being no high, separating walls 

 between them as in C. jezvettii. When this feature is well preserved, 

 as in a not fully mature specimen in Dr. Walker's collection and in 

 the tvpes of C. tripectinatus and Apiocystitcs canadensis, it is very 

 striking. That the ambulacra in this species more often remain 

 simple has no marked value, because some specimens have bifurcated 

 arms, and in C. jewettii fully mature examples are also seen to have 

 but 5 simple ambulacra. In a small but very fine, typical example of 

 C. canadensis, all the ambulacra bifurcate once except the one to the 

 right of the anus. In a larger but less typical specimen 4 of the 

 ambulacra divide, but in this case the simple one is to the left of the 

 anus. 



Billings distinguishes bis Apiocystites canadensis from A. elegans 

 Hall by the 5 arms and the rhombs "not double, but single, i. e., the 

 two triangles, of which each is composed, have their bases in contact, 



