St. Peter^s Sandstone. 



135 



an infinite number of minute vertical holes, about the size of 

 knitting needles. These are, perhaps, Scolithus tubes. In 

 Missouri, there is found a sandstone formed of columns per- 

 pendicular to the plane of deposit,* and these may also be 

 Scolithus tubes. 



Planolites sp. — A species of Planotites was found by the 

 writer in 1S89 at Fountain, Minnesota, in strata referred to 

 the St. Peter's. It is associated with Lingulepis morsensis and 

 Orthis sp., already noted, but it has not been referred to any 

 species. 



CEPHALOPODA. 



Orthoceras. — Fragments of Orthoceras, some of large size, 

 are noted as occurring in this sandstone in Missouri. J One 

 locality is in Maries County, + the specimen stated to be five 

 and one-half inches in diameter, while other specimens thirty 

 inches in diameter and ten feet long are found near the line 

 between Gasconade and Franklin Counties. In the roof of 

 a cave near Marthasville, circular rings, supposed to be cross 

 sections of Orthoceras, are noted. || It is possible that these 

 specimens really belong to the overlying Trenton. The 

 writer has collected large specimens of the genus from the 

 Trenton at Ripon, Wisconsin, in strata which were more 

 arenaceous than calcareous, and which might readily have 

 been referred to as a sandstone. 



The smalless of the number of species found in the sand- 

 stone is thus seen. Their occasional presence, however, may 

 be considered a proof that the formation is of mechanical ori- 

 gin and not a chemical precipitate. 



* Reports on the Geological .Survey of Missouri, 1855-1871. 1873, p. 55. 

 t .Swallow, G. C. Explanations of the Geological Map of Missouri, etc. Am. 

 Asso. Adv. Sci. Proc, Vol. XI, Part 2, 1S58, p. 17. 



X Reports of Geological .Survey of Missouri, 1855-1871. 1873, P- IO - 

 || Ibid, p. 55. 



