ORISKANY FAUNA OF BECRAFT MOUNTAIN 47 



crossed by regularly concentric fimbriae of short spinules, and between 

 these rows the surface is studded with granules so regularly arranged 

 that they seem to have been produced by the breaking up of radial 

 lines by intersections. 



Very recently Dr H. Scupin has discussed the variations of this 

 specific type occurring in the two Americas and South Africa 1 restrict- 

 ing the term Sp. arrectus to the forms figured by Hall in the work 

 cited, excluding figures le and If on plate 97. From a consideration 

 of these figures only it might seem that there is a varietal difference 

 in the specimens here referred to, .the one form having five or six lateral 

 plications and a more prominent median fold, while the latter (fig. le 

 and If) has seven or eight lateral plications, an apparently lower 

 median fold, and seems to be a shell of larger habit. It would be a 

 difficult matter to separate the specimens of this species occurring in 

 the Oriskany sandstone on the basis of these features. The degree of 

 plication is variable within the limits specified, and the prominence of 

 the median fold as well as the apparent size of the shell dependent 

 on the mode of retention. Determinations based on none too good 

 illustrations and fortified mainly by the study of internal casts will not 

 prove of practical usefulness in this case. Among the forms of this 

 shell found in the Oriskany fauna the transitions from one expression to 

 the other are so frequent as to make it practically certain that these 

 differences are altogether fugitive. 



I adopt without hesitation Castelnau's early term, Sp. murchi- 

 soni for this species, following Mr Schuchert's suggestion; for though 

 the figures given by Castelnau are for the most part extremely obscure, 

 no doubt can attach to his intentions and demonstration in this case. 



In accordance with his determination, Dr Scupin proposes to restrict 

 the term arrectus to shells represented in Paleontology of New 

 York as cited, exclusive of le and If, and regards these identical with 

 Sp. antarcticus Morris and Sharpe, a shell collected by Darwin in 

 the Falkland islands. These he would term Sp. arrectus var. 



'Ueber exotisclie, znr gruppe dcs Spirifer primaevus gehorige Formen ; Zeitschr. 

 der Deutsch. geol. Gesselsch, 1899. 50 : 462. 



