Pkossek and Cumings— Lower Silurian Sections. 



limestone of A 9 forms the upper part of the cliff, while the thinner lime- 

 stones of A 8 form the middle and lower part of the cliff. The following 



species were collected in A 8 . 



1. Mbnticidipora (JPrasopora) lyeoperdon (Say). (c) 



2. EscJi-aropora recta, Hall. (r) 

 .'5. Trematis terminalis (Emmons), Hall. (r) 



4. Rajinesquina alternata (Con.), II. and C. (c) 



5. Rajmesquina alternata var. riaswta, Con. (r) 

 (i. Rajvmsquina deltoidea (Con.), H. and C. (r) 



7. Strophomena cf. Scqfieldi, Winch, and Schuch. (r) 



8. Orikis (Platyspr'ophicb) hiforata (Schl.), Bill. (c) 

 0. Ortlds (JDalmwielld) testudmaria, Dal. (aa) 



in. Plectamhonites sericea (Sowb.), Hall. (a) 



11 Zygospira recw*virostra, Hall. (r) 



12. Asaph/m platyceplialu^ Stokes. (c) 



13. Oalymene callicephala, Green. (c) 



14. Oerav/rus phurexanthemus. Green. (r) 



15. Leperditia fabulites, Con. (r) 

 1(>. E/ndoceras proteiforme, Hall. (r) 



17. Orthoceras, sp. (r) 



18. JBellerophon hilobatus (Sowerby). (r) 



19. Dendrocriniis gracilis (Hall). (aa) 



20. Crinoid segments. 



A 9 . Massive grey Trenton limestone of the Prospect quarries, -Jl% 

 twenty-six feet thick in quarry on north side of creek near Prospect, burned 

 for quicklime and also used as a construction stone. It forms the top of the 

 steep cliffs along the upper gorge from the Adirondack railroad bridge to a 

 point above the highway bridge at Prospect. This massive crystalline lime- 

 stone in moderately thick layers, contains numerous fragments of fossils, 

 though the number of perfect specimens is small; while in the thin, black, 

 shaly layers fossils are common. This zone corresponds to D 28 , of White, 

 which is given as twenty feet thick. Conrad, in 1837, stated: "North of 

 Trenton Palls there is a capping of grey crinoidal limestone,"* and he 

 undoubtedly referred to this division of the Trenton limestone. 



1. Montivulipora (Prasopord) lyeoperdon (Say). (a) 



2. Stictopora cf. acuta, Hall. (r) 



3. Dend?'ocrinus gracilis (Hall). (c) 



* First Annual Report Geological Survey, Third District, New York (Assembly Document No. 161 \ p. 1G4. 



40 



