1870. ""^ ' [Wincliell. 



1. The MarsLall Group of Micliigau. 



2. The Gritstone and Waverly series of Ohio, down to the Chocolate 

 Shales. 



3. The Goniatite Limestone of southern Indiana, and its equivalent 

 sandstone in northern Indiana. 



4. The Kinderhook Group of Illinois. 



5. The Yellow Sandstone series of Iowa, at least down to the bluish 

 sandy shales. 



6. The series known in Missouri as the Chouteau Limestone, the Ver- 

 micular Sandstone and Shale, and the Lithographic Limestone. 



7. The Silico-bituminous Shales at the base of the Silicious Group of 

 Tennessee. 



For the sake of brevity and convenience I shall hereafter employ the term 

 Marshall Group as the general designation for this formation in the West- 

 ern States. 



Let us next consider what are the paleontological relations subsisting 

 between the Marshall Group and the Chemung and Portage and older for- 

 mations of New York. 



Professor Hall I'sj^^s described from Summit County, Ohio, a crinoid 

 under the name of Forbesiocrinus comviunis, which, he states, cannot be 

 distinguished from a single specimen from the Chemung of Chatauque 

 County, N. Y. At the same time he states that this species combines 

 some of the characters of two types occurring in the Carboniferous Lime- 

 stone. Another species, Forbesiocrinua lobatus, presents characters which 

 he regards as constituting a variety ( Var. tardus) of a species from the 

 Hamilton Group"^ . A third species from the same locality, he regards 

 as closely related to Poteriocrinus diffusu.% of the Hamilton Group, though 

 distinctly differing. At the same time Professor Hall notes no less than 

 seven species from this locality which exhibit distinct affinities with spe- 

 cies from the Burlington Limestone. We have in this assemblage of cri- 

 noids, therefore, two species identitied with species from rocks which I 

 regard as older than the Marshall, while nine species, including the two 

 identified, sustain intimate relations with the fauna of the Carboniferous 

 system, which Professor Hall assumes to be entirely above the zone of the 

 Chemung. 



The only other species from the Marshall Group which stand referred to 

 strata as old as the Chemung are the following : 



1. St7-ophoviena aixtastriata iLM, from. HohhieviWe, 'N. Y., — doubtfully 

 recognized at Cuyahoga Falls, Ohio. 



2. Orthis Vanuxemi, Hall, which if not identical with 0. MicJieUni 

 L'Eveille, a carboniferous species, is so closely related as to show that 

 the type of 0. Michelini began to exist during the Hamilton period. 

 A species perhaps identical, has been described from Iowa as 0. Sioallowi, 

 Hall ; and 0. flava, Win. from the same locality, belongs to the same 

 group of forms. 



"6 xvii. Rep. N. Y. Regents, p. 50. 



'" The analogue of this is i^. ffjrfdingj of the Carboniferous Limestone. Hall.xv'ReD X Y Re'' 

 12+. ,...„. 



A. P. S. — VOL. XI. — 22e 



