548 Annals of the Carnegie Museum, 



part of the section, where it has a range of about 150 feet, disappear- 

 ing a hundred feet below the top. At ("hazy, on the contrary, it is 

 one of the commonest fossils in a zone 1 10 feet in thickness and about 

 200 feet above the base of the section exposed there. ( That is, about 

 350 to 400 feet above the actual base of the formation.) 



Biicania sulcatiiia, at Valcour Island, is most common in a 20-foot 

 zone 345 feet above the base and again in a 100-foot zone beginning 

 a little below the range of Caiuaratircliia plena. At Chazy it is most 

 common in the faunule with Scalitcs aiigiilatus, 200 feet above the 

 base of the section. It does not become prominent above that hori- 

 zon, but specimens are found all through the section. 



Macluntes magnus has a comparatively restricted range in which it is 

 common, although single specimens have been found at almost all levels. 

 At Valcour Island it is common from the 345-foot level to the 700-foot 

 level, a range of over 350 feet. At Chazy it ranges from the 430-foot 

 level to the 615-foot level, only 185 feet of strata in which it is a 

 common fossil. 



Eoharpes aufiqiiatiis is not a very common fossil on Valcour Island, 

 but it may be said that it does not occur in the lower 150 feet, or in 

 the upper 200 feet. At Chazy it occurs near the middle of the mass. 



LoncJiodomas ha/// likewise does not occur in the lower 150 feet, but 

 is found all through the range of Mac/i/rifes mag/ius. 



F/ioincrops canadensis is absent from the sandstones and most of the 

 pure limestones, but may be found in almost any horizon where there 

 is mud, and it occasionally occurs in great abundance in the pure 

 dolomite of the reefs. 



Isote/us /larrisi, Tlia/eops ovata and ///cenns g/o/wsus are found all 

 through the .section and are of no value as horizon markers. 



Leperditia canadensis and Ei/ryc/ii/ina /a/i/nargina/a are also common 

 all through the section. 



Leperditia /iniatu/a, is, however, confined to a fairly definite range 

 of a little over 325 feet, beginning at a horizon 375 feet above the base. 



Division of t/ie C/iazy Section. 



The study of the range of species in the Chazy sections shows that 

 it is possible to divide the formation there into three great divisions, 

 as at Valcour Island. 



Brainerd and Seely have also divided the Chazy formation into 

 three divisions, depending upon a combination of lithologic characters 



