BUFFALO SOCIETY OF NATURAL SCIENCES 95 



seems to be unnecessary. The annelids surely would be more natu- 

 rally accounted for as terrestrial forms and besides, it would scarcely 

 be possible for them to leave their trails in deposits formed under 

 water. Such trails would have to be made on surfaces exposed to 

 the air long enough to harden and to be covered by wind-blown sand 

 or dust or by a fresh deposit of water-laid material, but in the latter 

 case a sufficient length of time would have to elapse to allow of the 

 thorough hardening of the trail. In this case as in many another the 

 question must be raised: Why if the eurypterids were marine were 

 they the only organisms which were carried in from the open sea? 

 It is well known that the littoral waters of the Pre-Cambric must have 

 teamed with all the forms of life which are so abundantly represented 

 in the advancing Cambric waters. It seems absurd to suppose that 

 thousands of fragments of a eurypterid should have been washed in 

 from the sea, but no other marine form. 



The great thicknesses of Algonkian limestone found in the Belt 

 terrane and corresponding formations have been adequately account- 

 ed for by Walcott as algal deposits in a series of lakes formed within 

 the CordiUeran geosyncline. "The lakes of Algonkian [Pre-Cambric 2 ] 

 time were not much if any larger in area than the 'Great Lakes' of 

 the St. Lawrence drainage basin and they were much shallower and 

 more laden with mud and mineral matter in solution. 



"The area of the Belt terrane in Montana is about 6000 square 

 miles. This seems large when studying it in the field, but it is only 

 one-fifth of the size of our great fresh -water Lake Superior" (290, 



89)- 



Walcott has described nine species of calcareous algae from the 

 Newland limestone below the Greyson shales and one which is abun- 

 dant in the Spokane shales just above the Greyson. It is much more 

 logical to suppose that the Greyson shales represent river rather than 

 marine deposits, for they are coarse and arenaceous with interbedded 

 shales, in which algal reefs could not grow. This would account for 

 the absence of the reefs in the Greyson and for the absence of the 

 eurypterids in the Newland limestone. I make this suggestion merely 

 as a more plausible explanation of the conditions than the one which 

 is usually offered. 



If it can be assumed as proved that the remains in the Belt 

 Terrane are of eurypterid affinity, they would offer just the proof 



2 The Belt terrane is considered by Professor Grabau as representing a pre-Cambric Palaezoic 



terrestrial deposit lying above the true Algonkian. 



