Petra. 



628 



plate 5, (H) figs. 3 (55 to 3 ^; found in the Meniicus {Niagara) 

 limestone of Middle Tennessee. Vh. 



Petraia waynensis, SafF. Geol. Tenn., 1869, page 314, 320, 



CeoUlLVoLZFlate^h^ 



plate 5j (H.) tigs. 15 ^, to iJ li ; common in and characteristic of 

 the Meniscus "sponge bearing" {Niagara) beds of Middle 

 Tennessee. F5. 



Petrodus occidentalis. New. & Wor. Geol. 111. Vol. 2, 



Xin -'^ IS. y^^ 2.' 866, page 70, 



plate 4, figs. 

 15, 15 a, 15 h 

 top and side 

 views of two 



specimens offish-teeth (?) 16, 16 a, a supposed variety of the 

 same species, which is much like P. patelliformis^ McCoy, 

 from the Irish Mountain limestone. Agassiz suggested that 

 these were not teeth, but tubercles on the skin of the fish, like 

 the shagreen of the Sharks, and Kays ; their bases show that they 

 could not have touched each other as teeth do. They difi<er 

 wonderfully, some being ten times as large as others, some 

 circular, some oval, some with sharp points and ridged, others 

 nearly smooth. Belleville, 111. Coal measures. XIIL 



Petrolystra gigantea, Scudder. An insect found in the 

 tierh ^^^ Oligocene tertiary hed of Florissant, Colorado. 



Figure taken from Zittel's handbuch der Palae- 

 onthologic, fig. 992 natural size, — Tert, 



992:. 



Zirref, 



