CONTEMPORARIES AND SUCCESSORS OF EOZOON. 133 



laminated sediment, sliows perforations of various 

 sizes, somewhat scalloped at the sides, and filled with 

 grains of rounded silicious sand. In my own collec- 



I'on there are specimens of micaceous slate from the 

 ime region, with indications on their weathered sur- 

 ges of similar rounded perforations, having the 

 aspect of Scolithus, or of worm-burrows. 



" Though the abundance and wide distribution of 

 Eozoon, and the important part it seems to have acted 

 in the accumulation of limestone, indicate that it was 

 one of the most prevalent forms of animal existence in 

 the seas of the Laurentian period, the non-existence of 

 other organic beings is not implied. On the contrary, 

 » independently of the indications afforded by the lime- 

 stones themselves, it is evident that in order to the 

 existence and growth of these large Rhizopods, the 

 waters must have swarmed with more minute animal 

 or vegetable organisms on which they could subsist. 

 On the other hand, though this is a less certain infer- 

 ence, the dense calcareous skeleton of Eozoon may 

 indicate that it also was liable to the attacks of animal 

 enemies. It is also possible that the growth of 

 Eozoon, or the deposition of the serpentine and pyrox- 

 ene in which its remains have been preserved, or both, 

 may have been connected with certain oceanic depths 

 and conditions, and that we have as yet revealed to us 

 the life of only certain stations in the Laurentian seas. 

 Whatever conjectures we may form on these more 

 problematic points, the observations above detailed 

 ppear to estabUsh the following conclusions : — 



