LOWER SILURIC SHALES OF THE MOHAWK VALLEY 21 



4 Triarthrus becki Green (c) 



5 Graptolites (a) 



6 Asaphus platycephalus Stokes (r) 



7 Tellinomya nuculiformis Hall (r) 



8 Pterinea trentonensis {Conrad) (rr) 



9 (?) Edmondia subtruncata {Hall) (rr) 



10 Endoceras proteiforme Hall (c) 



11 Raphistoma lenticulare {Emmons) (r) 



12 Trocholites ammonius Conrad (r) 



13 Rafinesquina alternata {Con.), H. and C. (r) 



14 Orthis (Dinorthis) pectinella Emm., var. semiovalis, 



Hall (rr) 



15 Crinoid segment (rr) 



16 Leptobolus insignis Hall (r) 



17 Lingula curta Con. (a) 



18 Monticulipora (Prasopora) lycoperdon Say. (rr) 



19 Bellerophon sp. (rr) 



With the exception of a bed of compact barren limestone at the 

 base, which has an irregular surface and is separated by an uncon- 

 formity from the overlying beds, the Trenton is composed of thin 

 beds of limestone alternating with layers of shale of equal thick- 

 ness, the whole having a distinctly transitional character like the 

 beds designated as Dolgeville beds by Gushing. A limestone near 

 the base is a shell-breccia and contains the brachiopods and trilo- 

 bites cited by Prosser. This is followed by a thin bryozoan reef, 

 from which Doctor Ulrich has identified: 



Stictoporella cf. angularis Ulrich 



S. exigua Ulrich 



Phaenopora incipiens Ulrich 



Pachydictya acuta {Hall) 



P. pumila Ulrich 



Eridotrypa mutabilis var. minor Ulrich 



A small reef of broken shells swept up by a current, passes 

 through the shaly Trenton limestone. This is especially rich in 

 fossils and has furnished {fide Doctor Ulrich) : 



Corynotrypa inflata (Hall) 

 Atactoporella ? crassa Ulrich 

 Stomatotrypa ? sp. 



Eridotrypa mutabilis var. minor Ulrich 

 Phylloporina reticulata {Hall) 

 Nematopora ovalis Ulrich 

 Arthroclema pulchellum ? Billings 

 Rhinidictya canadensis Ulrich 

 Pachydictya acuta {Hall) 



