PROTOZOA. FORAMINIFERA. 21 



in a plane spiral. Each whorl completely encloses the 

 preceding one, by means of the lateral prolongations of 

 the chambers, so that externally only the last whorl of 

 the shell is visible. The whorls are divided into chambers 

 by septa which are slightly curved backwards ; each 

 chamber communicates with the neighbouring one by 

 means of a median fissure placed next to the margin of 

 the previous whorl. Each septum is formed by two 

 lamellae. A supplemental skeleton is present, the larger 

 part of it forming what has been termed the ' marginal 

 cord.' The general shell-substance is minutely perforated, 

 and a system of canals also traverses the septa and supple- 

 mental skeleton. Carboniferous Limestone to present 

 day. It attains its maximum in the Eocene, only one 

 or two rather rare forms are living, one of which (N. cum- 

 mingi) is found in shallow water in tropical and sub- 

 tropical regions. 



EOZOON. In the year 1864 the name Eozoon cana- 

 dense was given by Dawson to a peculiar body found in 

 the Laurentian rocks of Canada, and referred by Dr Car- 

 penter and himself to the Foraminifera. Other 'species' 

 were subsequently found in Bavaria, Bohemia, Silesia and 

 elsewhere. 



The Laurentian rocks of Canada consist of two divi- 

 sions, an upper and a lower. The thickness of the lower 

 is estimated at 20,000 feet; it is composed of gneisses 

 and schists, with intercalated beds of crystalline limestone. 

 In the latter, Eozoon occurs, frequently having the form 

 of extensive sheets or masses ; but according to Dawson, 

 recently collected examples " have established the fact 

 that the normal shape of young and isolated specimens of 

 Eozoon canadense is a broadly-turbinate, funnel-shaped or 



