NIAGARA FALLS AND VICINITY 



197 



Fig. 114 Atrypa rugosa with striae enlarged 



"being almost flat. Strong sinus and fold in adult, with minor plica- 

 tions on each; strong concentric 

 rugose lamellae; plications less 

 rounded than preceding. 



Found in the Clinton and 

 Rochester beds at Niagara, gen- 

 erally associated with the preced- 

 ing but much less common. Also 

 at Lockport, etc. (Hall). 



Genus cyrtina Davidson 



[Ety. : y.opzia^ a wicker shield] 



(1858. British Carbon. Brachiopoda. Monograph, p. 66; 1S93. 

 Pal N. Y. V. 8, pt 2, p. 43) 



Shells S p i r i f e r -like; usually small; valves very unequal; 

 pedicle valve elevated, with a high cardinal area, the delthyrium of 

 which is covered by an elongate, convex pseudodeltidium, which is 

 perforated below the apex; surface plicate. Dental lamellae strong, 

 converging rapidly, and meeting a median septum. Cardinal pro- 

 cess a double apophysis. Brachidium an extroverted spire. 



Cyrtina pyramidalis (Hall) (Fig. 115). 



Spirifer pyramidalis Hall (1852. 



Pal N. Y. 2:266, pi. 54) 



Distinguishing characters. Pyramidal 



form; vertical or slightly bent area; nearly 



flat brachial valve; extremely convex ped- 



Fig. 115 Cyrtina pyramidalis with iclc valvc ; subaugular pHcatious, about 



.striae enlarged 



five on each side of mesial fold and sinus. 

 Found " near the top and just below the edge of the cliff on the 

 Niagara river above Lewiston " (Hall). 



;> 





Genus spirifer Sowerby 



[Ety.: spira, spire; fcro, to bear] 



(1815. Mineral conchology, 2:42; 1894. Hall & Clarke. Pal. 

 N. Y. V. 8, pt 2, p. i) 



Shell variously shaped, commonly very much wider than long, 

 radially plicated or striated, crossed by concentric growth lines, 

 which in some forms are lamellose or even marked by spines. 



