CONTEMPORARIES AND SUCCESSORS OF EOZOON. 157 



porous kinds are not very dissimilar from calcareous 

 sponges^ but they generally want true oscula and 

 pores, and seem better adapted to shield the gelati- 

 nous body of a Foraminifer projecting pseudopods in 

 search of food, than that of a sponge,, living by the 



Tig. 42. Stromatopora rugosa, Hall — Lower Silurian, Canada. 

 {After Billings.) 



specimen is of smaller size than usual, and is silicified. It is probably 

 inverted in position, and the concentric marks on the outer surface are due 

 to concretions of silica. 



introduction of currents of water. Many of the 

 denser kinds, however, have their calcareous floors so 

 solid that they must be regarded as much more nearly 

 akin to Foraminifers, and some of them have the same 

 irregular inosculation of these floors observed in Eo- 



