Raymond : Thr Chazy Formaiion and its Fauna. 547 



Discussion of ilie Juiuiias of flic Chazy and Valcour Island Sections. 



On tabulating the preceding lists to obtain a comparative view, 

 there are certain things which are noticeable in regard to the range of 

 the fossils. 



Cxstids do not occur in the lowest hundred feet. 



Bryozoa, while they begin to appear in the lower portion, are more 

 abundant toward the middle and top. 



Lingn/a hrainerdi is confined to the basal sandstones. 



CamarotoecJiia plena is absent from the lower 700 feet and has a 

 range of 150 to 175 feet at the top. 



Zygospira aci/tirosfris, at Valcour Island, is most common in the 

 lower part of the section, but at Chazy occurs quite commonly in the 

 lower part of the range of Maclurites niagnns as well. 



Rafinesquina cJiamplainensis is absent from the lower 100 feet and 

 the u])per 200. In never occurs with Ca/narota'chia plena. 



Rapinesqiiina iiicrassata becomes most common well up in the 

 section, at about 600 feet above the base, and occurs to some extent 

 with Caniaroto'cliia plena, although more common below the range of 

 that species. 



Plcesioniys platys is rare in the lower 350 feet and seldom occurs in 

 the upper 150 feet, its range being comparable to that oi Rajinesqnina 

 cliamplaincnsis. 



OrtJiis acutiplicata is confined to the lower layers on Valcour Island. 



Hebericlla vuli:;aris is not common in the lower 100 feet, but is a 

 common fossil from that point to within a hundred feet of the top. 

 In the lower part of the range of Caniarotcechia plena, Hebertella 

 vulgaris is its constant and abundant associate, but the species is 

 almost absent in the upper hundred feet where Cainarofo'cliia plena 

 reaches its greatest development. 



Camcrella longirostris does not occur in the basal standstones, but 

 may be found at almost any horizon above them. 



Camerella varians does not appear in the first three hundred feet, 

 and is not often found with Caviarota-cliia plena. 



Pelecypods and gastropods are almost absent from the lower 300 

 feet at Valcour Island. 



Modiolopsis fabaforniis is the only horizon marker among the pele- 

 cypods. It is an almost constant associate of Camarotoechia plena in 

 the upper 100 feet. 



Raphistonia stainineum is common at Valcour Island in only the ui)})er 



