CONTEMPOEAEIES AND SUCCESSOES OP EOZOON. 151 



tlius bridge over much of the apparent gap in the life 

 of these two great periods. 



Only as yet on the coast of Labrador and neigh- 

 bouring parts of North America, and in rocks that 

 were formed in seas that washed the old Laurentian 

 rocks, in which Eozoon was already as fully sealed up 

 as it is at this moment, do we find Protozoa which 

 can claim any near kinship to the proto-foraminifer. 

 These are the fossils of the genus Arcliceocyathus — 

 " ancient cup-sponges, or cup-foraminifers," which 

 have been described in much detail by Mr. Billings 

 in the reports of the Canadian Survey. Mr. Billings 

 regards them as possibly sponges, or as intermediate 

 between these and Foraminifera, and the silicious 

 spicules found in some of them justify this view, un- 

 less indeed, as partly suspected by Mr. Billings, these 

 belong to true sponges which may have grown along 

 with Archseocyathus or attached to it. Certain it is, 

 however, that if allied to sponges, they are allied also 

 to Foraminifera, and that some of them deviate alto- 

 gether from the sponge type and become calcareous 

 chambered bodies, the animals of which can have 

 differed very little from those of the Laurentian Eozoon. 

 It is to these calcareous Foraminiferal species that I 

 shall at present restrict my attention. I give a few 

 figures, for which I am indebted to Mr. Billings, of 

 three of his species (figs. 38 to 40), with enlarged 

 drawings of the structures of one of them which has 

 the most decidedly foraminiferal characters. 



To understand Arch^ocyathus, let us imagine an 



