CAMBRO-ORDOVICIAN LIMESTONES 709 



Few fossils have been found in this formation, except in the middle 

 chert-bearing portion. These consist chiefly of gasteropods, ostra- 

 coda, cephalopods, and bryozoa. A few ostracoda {Leperditia jahu- 

 lites) and Tetradium " syringoporoides^^ can usually be obtained 

 from the fine even-grained beds in all parts of the formation; 22 

 species were obtained from the subgranular beds of the middle 

 division, and the following have been tentatively identified by Mr. 

 Ulrich: 



Stromatocerium sp. nov. Dinorthis cf. platys. 



Tetradium "syringoporoides" — the Strophomena aff. S. charlottae. 



single-tubed form of this genus so Bucania sulcatina. 



characteristic of the Stones River. Maclurea magna. 



Glyptocystites sp. undet. Lophospira bicincta. 



Lingulella ? belli (Billings) Isochilina cf. amiana. 



Hebertella borealis. Ampyx halli. 

 H. vulgaris 



The massive shells and opercula of Maclurea magna are the most 

 characteristic fossils of this division. From the standpoint of cor- 

 relation the most noteworthy feature of the above list is that no less 

 than eight of the species occur in the middle Chazy of the Cham- 

 plain Valley. 



Although only Leperditia fabulites, L. cf. amiana, and Lingula 

 manteli were obtained from the lower beds of this formation in this 

 area, 1 2 species were collected 30 miles down the valley at Martins- 

 burg, W. Va., by Mr. Ulrich and the writer, of which the following 

 have been determined: 



Solenopora compacta var. Lophospira cf. perangulata. 



Cyrtodonta sp. nov. Helicotoma ? sp. nov. 



Matheria sp. nov. Oncoceras ? sp. undet. 



Liospira cf. obtusa. Leperditia fabulites. 



The fossils as well as the lithologic character of this formation are 

 so nearly the same as those of the Stones River limestone of Tennessee 

 that they are regarded by Mr. Ulrich as identical, and the name 

 Stones River is therefore applied. 



CHAMBERSBURG LIMESTONE 



The Chambersburg limestone is the uppermost division of the 

 Shenandoah limestone. It is characterized throughout the area by 



