TROPIDOLEPTUS CARINATUS IN CHEMUNG FAUNA 347 



This recurrent Hamilton fauna was collected in Bath County, 

 Virginia, near Mountain Grove post-office. The relationship 

 which it bears to the other faunas which are known in the section 

 from which it comes will be indicated by the following section of 

 the rocks exposed along Little Creek at Mountain Grove post- 

 office. 



SECTION AT MOUNTAIN GROVE, VA. 



Feet 



h. Thin-bedded, hard, gray sandstone and interbedded shale 700 



g. Thin-bedded, hard, gray sandstone and interbedded shale 100 

 /. Rather hard, sandy, dark-blue shale and some thin bands 



of sandstone with Portage fauna 600 ± 



e. Black, hard fissile shale 100 



d. Covered 70 



c. Hard, black, and dark greenish-gray calcareous shale 6 



b. Black, blocky, tough shale 20 



a. Dark, coarse, ferruginous sandstone with frequent concre- 

 tions of pyrites (Oriskany) 20-f- 



The sandstone at the base of the section holds the usual type of 

 Oriskany fossils and clearly represents the Oriskany sandstone. 

 The fauna of the lower 26 feet of calcareous and blocky shale is 

 rather meager in this section as compared with the rich fauna often 

 found at this horizon. The species collected from it are the 

 following : 



FAUNULE c, MOUNTAIN GROVE, VA. 



Orbiculoidea lodiensis media , a 



Anoplotheca acutiplicata c 



Conularia sp r 



This faunule taken alone, of course, could hardly be cited as sat- 

 isfactory evidence of a definite horizon. An extended study 1 of 

 the fauna found at this horizon by the writer throughout an exten- 

 sive region in the Allegheny Mountains has shown, however, 

 that the horizon is that of the Onondaga limestone. The greater 

 part of the Hamilton horizon is covered in the section. 



The next higher fauna which was collected from this section is 

 shown in the following list of species from the lowest beds in the 

 sandy shales marked / in the section outcropping at Cash's store. 



1 The Onondaga Fauna of the Allegheny Region, Bull. U.S. Geol. Survey (in press). 



