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NEW YORK STATE MUSEUM 



D i ]> 1 o g r a p t u s foliaceus var. t r i f i d u s is either identical with or 

 but little different from D . foliaceus var. calcaratus Lapworth. 

 This evidence is, of course, by no means sufficient to infer a closer connec- 

 tion of the Arkansas sea with the far-off British embayment of the North 

 Atlantic, for it is to be noted that the forms mentioned are varieties of much 

 varying and widely distributed species and may hence be convergent or 

 parallel forms developed independently in different provinces ; and further 

 Dicellograptus divaricatus and Diplograptus foliaceus 

 var. calcaratus do not appear in Great Britain until the Hartfell shale 

 stage. If they are not parallel but identical varieties, the suggestion could 

 be made that the western sea stood in connection with the northeastern 

 embayments of the North Atlantic sea by means of the Arctic ocean and 

 the Baltic sea, the latter of which has also furnished Diplograptus 

 foliaceus var. calcaratus (in Scandinavia) 1 , the forms having orig- 

 inated in the Pacific basin and reached the North Atlantic and Baltic basins 

 later on. 



From collections made by Ulrich in the shales associated with novacu- 

 ite in the Talihina formation of the Ouachita mountains in Indian Terri- 

 tory, I infer that a horizon in close proximity to that of the Dicellograptus 

 shale occurs there. One of the collections [loc. 240] contains: 

 Dicellograptus divaricatus var. bicurvatus D. foliaceus var. (closely related to D. 

 nov. crassitestus nov. and probably 



Diplograptus foliaceus Murchison identical with 1 >. tr if id us Gurley) 



Climacograptus cf. antiquus Lapworth 



Another [loc. 240a] has furnished : 

 Dicellograptus divaricatus var. rigidus Climacograptus bicornis var. tridentatus 



Lapworth Lapworth 



Dicranograptus ramosus Hall 



The occurrence of the variety of D i p 1 . foliaceus probably rep- 



1 See chart in part 1 of this monograph [Mem. 7, P.4SS ] which will, with slight changes, 

 also serve to illustrate the present discussion in view of the continuous deposition cf 

 graptolitiferous beds during Champlainic time in the same regions. 



