l8o NEW YORK STATE MUSEUM 



one in the axial line. Hall & Clarke [Palaeontology of New York, 1894, 

 V. 8, pt 2, pi. 30, fig. 8] referred S. unicus to S. arenosus, but there 

 is on this shell and that which served as the type ofS. superbusa con- 

 cordance of minor differentials not seen in the typical forms of S. are- 

 nosus of the New York Oriskany nor in the representatives of the species 

 in the Grande Greve limestones. 



We have observed only three examples of this type in the latter, and 

 none so good as Billings's specimen but they are all at once distinguishable 

 from their associates by the features mentioned. 



Localities. In the upper beds at Grande Greve and Indian Cove. 



Spirifer fimbriatus (Conrad) 



Plate 32, figures 11-13 



Delthyris fimbriatus Conrad. Acad. Nat. Sci. Phila. Jour. 1842. 8:263 

 Spirifer fimbriatus Hall. Palaeontology of New York. 1867. 4:214, pi. 33, 

 fig. i-ii 



It is no light task to determine specific distinctions, alleged and 

 actual, among the fimbriate-plicate Spirifers of this particular stage in the 

 history of the genus in the ordinary state of their preservation. Spirifer 

 cyclop terus, S. fimbriatus, S. tribulis, S. murchisoni and 

 some others are such forms separated by distinctions which at times seem 

 quite conventional and yet each is fortified in typical expression by the sum 

 of its characters. The presence of Sprlfer fimbriatus (the type of 

 which is a Hamilton shell) in the Oriskany was indicated by Hall in the 

 work cited wherein a small fragment of the shell was figured. The species 

 proves to be common in excellent preservation in the deposits at Glenerie, 

 N. Y. and differs from the later expressions of the species only in the 

 stronger development of the plications. The history of the species as its 

 limitations are now drawn seems to involve obsolescence almost to extinc- 

 tion of the plications and this is due rather to an arrest of development in 

 later form than a distinct assumption of senile characters for in the earliest 

 Oriskany shells the plications are obscure in the umbonal parts but become 

 increasingly prominent with individual growth. 



Billings seems to have regarded the Gaspe representatives of these 

 shells as Sp. cyclopterus \loc. cit. p. 48, pi. 3 A, fig. 4, 4a] and to have 

 intended the same by the term Sp. crispatus used in Logan's Geology 

 of Canada, page 392. 



The Gaspe shells bear distinct similarity to Sp. tribulis which is 

 so closely allied to Sp. cyclopterus of the Helderbergian that Hall 

 suggested the latter might prove only a late representative of the former. 

 There are differences however. Spirifer tribulis is a more extended 

 shell with sharper plications and less equally convex and rounded valves 



