280 THE CAMBRIAN lm/u..8i. 



fossils in the limestone conglomerate have an Upper Cambrian aspect, 

 and include Lingida sp. ?, Agnostus sp.?, Amphion sp.?, Bathyurus sp. f 

 Below the horizon of the conglomerate and in situ in the shales, there 

 were found the genera Lingulella, Agnostus, Ptychoparia and Solenop- 

 leura. With the exceptiou of the Solenopleura the species appear to be 

 identical with those of the limestone lentile (9) of the Georgia section. 

 A section measured east of Swanton by Sir William E. Logan gave but 

 520 feet of the limestone (Red Sandrock) series. 1 But farther to the 

 north, nearly on the line of the Canadian boundary, he found 1,410 feet 

 of limestone in the section, proving that this portion of Cambrian ter- 

 rane thickens rapidly to the north. 



The section measured in the town of Georgia is the most complete yet 

 taken in Vermont (ante., pp. 278, 279). At the base a great belt of dolo- 

 mitic limestone 1,000 feet in thickness rests against, and, by an overthrust 

 fault, overlaps the Trenton limestone of the Lower Silurian (Ordovician). 

 W hat was originally beneath the Cambrian limestone is yet undetermined. 

 In the Highgate section the limestone belt is nearly 1,200 feet thick. The 

 base is unknown, and it does not appear, so far as 1 know, in the section 

 between the boundary of the United States and Canada and the out- 

 crop in the town of Georgia. I have suggested that the great mass of 

 shaly argillite east of the Vermont Central Railway track in the Georgia 

 section may be older than the limestone at the base of the section, but 

 until further evidence is obtained this is merely conjectural. 2 



During the field season of 1890 I studied the "Red Sandrock" series 

 of the Georgia section, and found a little to the south and at the base 

 of the original section that there was a band of buff-colored calcareous 

 sandstone some 50 feet in thickness. In the upper beds of this, Obo- 

 lella, like Obolella crassa, Hyolithes americanus, H. communis, H. sp. 

 undt., Hyolithellus micans, and fragments of Olenellus occur. In a lead- 

 colored magnesian limestone, passing into a buff-colored limestone 15 

 feet above the sandstone, fragments of Olenellus and the head of Pty- 

 choparia, apparently identical with P. trilineata, were found, and in the 

 superjacent pinkish magnesian limestone with interbedded drab-colored 

 limestone, at horizons of 85 feet, 113 feet, and 198 feet above the sand- 

 stone, fragments of fossils that I recognized as portions of Olenellus and 

 very perfect specimens of Salterella sp.? occur in the decomposed sili- 

 cious limestones. 



The discovery of the Olenellus fauna in the lower portion of this mag- 

 nesian limestone series gives the fauna a range through 1,000 feet of 

 limestone and the 250 feet of superjacent Georgia shale. 



The fragments and heads of the genus Olenellus that were found in the 

 lower beds were not sufficient to determine whether it was the equiva- 

 lent of the Olenellus asaphoides of tlie Washington County section or not. 



1 Geological Survey of Canada: Report of progress from its commencement to 1863. Montreal, 

 1863, p. 281. 



2 Walcott, CD. : Second contribution to the studies of the Cambrian faunas of North America. 

 U. S. GeoL Surv., Bull. No. 30, 1886, p. 19. 



