214 





( Fig. 



121.) (Pnl. N. V 



Spirifek macronotus. Hall. 

 Vol. IV., p. 231, PI. XXXVIII. A.) 



Distinguishing Characters.— General resemblance to S. 

 audaculus (of which it may be only a variety), differing 

 from that species mainly in the very high, fiat, area, minute 

 beak, comparatively shallow mesial sinus, which rapidly 



FlG 121. Spirifer macronotus. Cardinal view of a lar^e individual; lateral views of 

 two individuals, showing the character of the area (from Hall). 



widens towards the front, and the number of plications, 

 which varies from fifty to seventv on each valve, of which 

 only three or four on each side of the fold and sinns reach 

 the beak: the delthyrium is more than twice as high as 

 wide, and the surface of the shell exhibits lamellose, imbri- 

 '•;i1 rag growth lines. 



Found in the Encrinal limestone, at Section 5 (common) ; 



Stictopora and Demissa beds, at Section 5 (common): one 



and one-half to three feet below the Encrinal limestone, at 



lion C) hare): shale below the Trilobite beds, in Avery's 



Ravine I rare ). 



Spirifer asper. Hall. (Fig. 122.) (Geol.Siirv.of Iowa. 

 1858, Vol. 1.. IM. II.. p. 508, PI. IV.) 



Distinguishing Characters.— Small size; sub-pyramidal 

 outline: high, flat cardinal area of pedicle valve; narrow 

 and high delthyrium; broad, comparatively shallow sinus, 



