41 



are common. The thorax, from it.s jointed condition, is 

 subject to greater destruction, and hence is not commonly 

 preserved. Nevertheless, complete and perfect specimens are 

 occasionallv obtained. The trilobite most common in this 

 bed is the ordinary Hamilton species Phacops rana (Green), 

 though Crvphaeus bootbi Green, the form with long spines 

 on both sides of the head, and with fringed tail, also occurs. 

 Other fossils are rare in this bed. Below it, is a somewhat 

 more compact calcareous layer three to four inches thick 

 and rather concretionary. In this layer fossils are rare. 

 Under it occurs the second trilobite layer, eight inches thick 

 and, like the upper one, it is a calcareo-argillaceous, and 

 somewhat arenaceous bed, sometimes becoming quite gritty. 

 This contains more fossils than the upper bed, but the trilo- 

 bites of both species are the only abundant forms. Below 

 this, and separating it from the lowest trilobite bed — which 

 latter is only exposed at low water at the extreme lower 

 end of the section — are two or three inches of fissile shale, in 

 which Athyris spiriferoides (Eaton) is especially abundant. 

 With it occurs a large number of the small cup coral 

 Streptelasma rectum Hall, these two, with an occasional 

 specimen of Spirifer mucronattis (Conrad), forming the only 

 important fossils of the bed. 



Onlv about six inches of the lowest trilobite bed are ex- 

 posed, the total thickness of that bed being about a foot. 

 Both species of trilobites are abundant, and good specimens 

 may be easily obtained. 



Nowhere in the entire Hamilton group of this region are 

 trilobite remains so abundant. The conditions of the sea 

 must have been particularly favorable for their development 

 at that period, so that their remains became entombed by 

 the thousands. That they were but slowly buried seems to 

 be indicated by the separated portions of the body, a condi- 

 tion probably brought about by long continued maceration 

 before burial. Trilobites probably never lived in very deep 

 water, and both the nature of the rock and the scattered 



