128 



THE DAWN OF LIFE 



though the canals themselves in the arrangement more nearly 

 resemble Calcarina, which is represented in Fig. 12. In its 

 superposition of many layers, and in its tendency to a heaped 

 up or acervuline irregular growth it resembles Polytrema and 

 TinoporuS) forms of a different group in so far as shell-struc- 

 ture is concerned. It may thus be regarded as a composite 

 type, combining peculiarities now observed in two groups, or 

 it may be regarded as representing one of these in another 

 series. At the time when Dr. Carpenter stated these 



FIG. 12. Portion of shell of Calcarina. Magnified, after Carpenter, 

 (a) Cells. (l>) Original cell wall with tubuli. (f) Supplementary 

 skeleton with canals. 



affinities, it might be objected that Foraminifera of these 

 families are in the main found in the modern and Tertiary 

 periods. Dr. Carpenter has since shown that the curious oval 

 Foraminifer called Fusultna, found in the coal formation, is 

 allied to both Nummulites and Rotalines ; and Mr. Brady has 

 discovered a true Nummulite in the Lower Carboniferous of 

 Belgium. I have myself found small Foraminifera in the 

 Silurian and Cambro-Silurian of Canada. This group being 



