SPIBIFER^ OF THE PORTAGE AND CHEMUNG GROUPS. 237 



SPIRIFER^ OF THE PORTAGE AND CIIEMUNG GROUPS. 



The shales and sandstones of the Portage group, within the limits of the 

 State of New-York, are generally very deficient in Brachiopoda, and but 

 a single species of Spikifer is at present known to me in this formation. 

 This one is more like the European Carboniferous Spirifera glabra, than 

 any of the Devonian species figured by Mr. Davidson in his Monograph 

 of British Devonian Brachiopoda. 



In the Chemung group, Brachiopoda are abundant, and Spirifbra is 

 very conspicuous among the other genera. Notwithstanding however its 

 abundance and wide distribution in this group, there are few species 

 known in the State, and of these, one only is common, the Spirifera verneuilt 

 = S. disjunda and its varieties, which extends from the southeastern 

 counties quite to the western limits of the State, and is equally abundant 

 in the adjacent portions of Pennsylvania along the southern and western 

 borders of New- York. 



I have heretofore recognized, with doubt, the Spirifer mucronatd* in 

 the Chemung group in the southern part of New- York ; but a critical 

 examination of all the specimens from authentic localities of that forma- 

 tion has shown that the fossils thus referred belong to the S. mesacostalis, 

 and no true example of S. mucronata is yet known to me from the Che- 

 mung group. 



It may be remarked in this place that the shaly sandstones or arena- 

 ceous shales of the Hamilton group in the southeastern part of the State 

 are lithologically similar to some of the Chemung beds, and not always 

 readily distinguishable therefrom. In these coarser beds of the Hamilton 

 group, the S. mucronata is often abundant in the condition of casts. 



• DeUhifrit mitcrofwrio? Geological Report of the Fourth District of New- York, p. 271. 



