198 NEW YORK STATE MUSEUM 



Hinge line generally long and straight; pedicle valve usually with 

 moderately high area, with an open delthyrium, the margins of 

 which are prolonged into stout simple teeth, supported by dental 

 lamellae. Area of the brachial valve the lower. A calcareous 

 brachidium in the form of a double spire, whose apexes are directed 

 toward the cardinal angles, nearly fills the cavity of the shell. 



Spirifer radiatus Sowerby (Fig. 116) (Hall. 1852. Pal. N. Y. 

 2:66, pi. 22, p. 265, pi. 54) 



Distinguishing characters. Moderately large size; pedicle valve 

 with strongly incurved beak, moderate area, and broad shallow 



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Fig. 116 Spirifer radiatus showing variation 



mesial sinus; flattened median fold; fine uniform radiating striae 

 covering all parts of the shell. 



Found in the Clinton limestones and lenses and in the lower and 

 middle Rochester shales at Niagara; sometimes abundant. Also at 

 Lockport and elsewhere (Flail). 



The shell varies greatly in form and proportions; sometimes the 

 hinge area is much extended or the hinge extremities are rounded 

 and the hinge line shorter than the shell below. Faint plications 

 near the fold and sinus also occur in some specimens, connecting 

 this species with the next. 



Spirifer niagarensis Conrad (Fig. 117) (Hall. 1852. Pal. 

 N. Y. 2:264, pi. 54) 



/•^^^ Distinguishing characters. Moderately 



r^ large size; convex, with nearly equal valves; 



I strongly incurved beak of pedicle valve; 

 moderate area; numerous fine, rounded, de- 

 pressed plications, which become obsolete 

 Fig.nTSpiriferniagarensis ^^^^^.^j ^j^^ extremities, and somctimcs ap- 

 pear quite flattened out on the surface; fine thread-like radiating 

 striae covering plications and interspaces alike. 



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