i899 C. CALLAWAY— ON EARLIEST LIFE 79 



not so minutely as in the Foraminifera. One or more 

 radial spines occur in some of the species ; and in two or 

 three of them an inner wall has been detected, connected 

 by rays with the outer shell. One objection to the 

 organic origin of these forms is their extreme minuteness, 

 their average diameter being only one-seventeenth of that 

 of one of the Palreozoic Radiolaria. For this and other 

 reasons we are unable to accept these specimens as 

 undoubted proofs of the co-existence of living beings. If 

 we could do so, we should have to regard them as the 

 oldest known forms of life. 



The Algonkian rocks of North America have yielded 

 Brachiopoda not unlike some of the Cambrian forms, and 

 obscure fragments of trilobites. The conical shells 

 which have been referred to the Pteropoda, have also been 

 detected. These types are so similar to the Lower 

 Cambrian fauna as to indicate that we are -still very far 

 from the base of the great life-succession. Associated 

 with these highly organised forms is Cryptozoon, which, 

 if organic, is a compound structure allied to the Forami- 

 nifera, and somewhat resembling the Stroniatopora of the 

 Silurian. 



We will now return to our British Upper Archccan 

 formations. Of the Uriconian there is little to be said. 

 It is usually of volcanic origin, consisting of lavas and 

 tuffs. No fossils could occur in the former, save under 

 very exceptional circumstances ; but organic remains are 

 sometimes found in volcanic rocks. However, the tuffs 

 of the Uriconian have not yielded fossil remains in anv of 

 the localities in which the rocks have been studied. In 

 some locahties the Uriconian is composed of ordinary 

 sedimentary strata ; but hitherto they have proved entirely 

 barren of life. 



There remains only the Longmyndian series, and it is 

 here, if anywhere, that we should expect to find some of 



