206 THE CAMBRIAN [bull. 81. 



tbin layer of the fucoidal sandstone. 1 In 1850 he called attention to 

 cylindrical masses from 3 inches to 15 and 20 feet in diameter that occur 

 in the Potsdam sandstone near Somerville, St. Lawrence County. 2 



The description and accompanying figure recall the Cryptozoon proli- 

 ferum described by Prof. Hall from the Potsdam formation of Saratoga 

 County. A year later attention was again called by Mr. Hough to the 

 cylindrical masses. 3 They are described as vertical cylinders from 2 

 inches to 20 feet and upward in diameter, and show a concentric struc- 

 ture. Numerous smaller bodies, not larger than an orange, of a sphe- 

 roidal stiucture are also met with in the vicinity. No traces of organic 

 life were observed in the matrix. It is evident that these bodies are 

 unlike the Saratoga Cryptozoon. 



A more extended definition of the Potsdam sandstone was given by 

 Dr. E. Emmons in 1856. He then included with it the lower sandstone 

 of the upper Mississippi Valley, and No. 1 of the Pennsylvania survey.* 



An excellent summary of the existing knowledge of the Potsdam 

 sandstone was given by Dr. J. J. Bigsby in 1858 in a paper on the Pa- 

 leozoic Basin of the State of New York. A description is given of the 

 mineral characters, mode of transition, stratigraphic position, mode of 

 occurrence, thickness, and paleontologic character. 5 



In a tabulation of the succession of sedimentary rocks Prof. Richard 

 Owen states that the Potsdam sandstone of New York geologists is con- 

 sidered by some English writers as belonging to a separate -system, the 

 Cambrian. 6 



The presence of the peculiar cylindrical masses in the Potsdam sand- 

 stone mentioned by Mr. Hough is also noticed by Mr. T. G. B. Lloyd in 

 Jefferson County, 7 but without any attempt to explain their origin or 

 nature. 



In a note on the geology of Port Henry, New York, Dr. T. S. Hunt 

 states that the Potsdam sandstone and the basal member of the over- 

 lying Paleozoic series is well seen in a railway cut near Port Henry. 

 The lower beds are massive and compact, dark bluish or iron gray, with 

 lighter bands and thin, blackish, shaly layers. The only fossils observed 

 were Scolithus linearis and 8. canadensis of the Potsdam of the Ottawa 

 Basin. 8 



1 Observations on the geology of Lewis County, New York. Am. Jour. Sci. and Agric, vol. 5, 1847, 

 p. 273. 



2 Catalogue of mineralogical and geological specimens received from F. B. Hough, 3d Annual Rep. of 

 Regts. Univ. State Cab. Nat. Hist, 1850, pp. 32, 33. 



3 On the cylindrical structure observed in Potsdam sandstone. Am. Assoc. Proc, vol.4, 1851. pp. 

 352-354. 



4 American Geology, containing a full statement of the principles of the science, with full illustra- 

 tions of the characteristic American fossils. Albany, 1856, vol.1, pt. 2, pp. 128-132. 



6 On the Paleozoic Basin of the State of New York. Parti. A synoptical view of the mineralogical 

 and fossil characters of the Paleozoic strata of the State of New York. Quart. Jour. Geol. Soc, Lon- 

 don, vol. 14, 1858, pp. 338, 339. 



6 Preliminary observations; general report and description by counties. (Lower and Upper Silu- 

 rian). Geological reconnaissance of Indiana, made in 1859-'60. Indianapolis, 1862, p. 14. 



7 Geological notes from the State of New York. Quart. Jour. Geol. Soc, London, vol. 32, 1876, pp. 78, 79. 



8 The geology of Port Henry, New York. Canadian Nat,, new ser., vol. 10, 1883, p. 421. 



