FORAMINIFERA. 



103 



stomella, but most characteristically in Calcarina (fig. 1*7, B), 

 and the stellate form of Tinoporus. This intermediate or 



Fig. 17. A, Diagram of one of the higher forms of the vitreous Foraminifera, showing the 

 double nature of the septa (6), the stolon-passages between successive chambers (a), and the 

 .supplemental skeleton (rf) ; B, Test of Calcarina Spengleri, magnified twelve diameters, show- 

 ing the spines formed by the supplemental skeleton ; c, Part of a section of the test of 

 Calcarina, magnified fifty diameters, showing the tubulated "proper walls" of the chambers 

 (?0, and the canal-system of the intermediate skeleton (d) ; D. Part of the test of Nummulina 

 Jcnvigata, highly magnified, showing the canal-system of the septa (s), and marginal cord (n). 

 (After Carpenter.) 



supplemental skeleton, wherever developed to any consider- 

 able extent, is traversed by a set of ' canals/ which are 

 usually arranged upon a systematic plan, and are sometimes 

 distributed with considerable minuteness " (Carpenter). The 

 canals of this system are doubtless filled in the living state 

 by prolongations of the sarcode, which serve to keep up the 

 vitality of the intermediate skeleton. This intermediate 

 skeleton, with its canal-system, is largely developed in many 

 of the highest and largest of the types of the Hyaline Fora- 

 minifera, and very specially so in the ancient Eozoon, if this 

 be rightly regarded as a Foraminifer. 



As regards the range of the Foraminifera in time, repre- 



