PRIi-CAMItklAN LIFE 



57 



Colorado Cailon in the Western United States, 

 VValcott has found a small roundish shell of uncer- 

 tain affinities,' a species of Hyolithes, probably a 

 swimming sea-snail or Ptcropod, a small fra-rnent 

 which may possibly have belonged to a Trilobite, 

 and some laminated forms which, if organic, are 

 related to the Cryptozoon already mentioned (Fig 

 14). 



The Kewenian series of Lake Superior has 

 yielded no fossils, but the pipcstonc beds of Minne- 

 sota, supposed to be about the same age, have 

 afforded a small bivalve shell allied to Lingula ; « 

 and the black shales of the head of Lake Superior 

 contain some impressions supposed to be trails of 

 animals.^ 



It has been a question whether the beds above 

 referred to should be regarded as a downward con- 

 tinuation of the Cambrian, or as the upper part 

 of an older system. Matthew, whose opinion on 

 such a subject is of the highest authority, regards 

 them as a distinct system, but as belonging, with 

 the Cambrian, to the great Paleozoic Period. Van 



' Discinoid or Patelloid. » Winchell. 



^ Selwyn and Matthew. 



