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[ Senate 



Chonetes hemispheric a ( n. s.). 



Pal. N.Y. Vol.iv. 



Shell transverse, semicircular, greatest width being along the 

 hinge-line ; ears extending beyond the body of the shell, and 

 distinct from it, but not flattened : dorsal valve unknown : 

 ventral valve extremely ventricose, forming, without the ears, 

 nearly a hemisphere ; umbonal region gibbous, and projecting 

 a little beyond the hinge. Surface marked by numerous regular 

 rounded, radiating, occasionally bifurcating strige. 

 The distinguishing features of this shell are its hemispherical form, pro- 

 minent gibbous umbonal region, and regular rounded striae about equalling 

 the intermediate grooves. 



Geological position and locality. Schoharie grit. 



Chonetes hemispherica. 



Chonetes AECUATA (n.s.). 



Pal.N.Y. Vol.iv. 



Shell semicircular, greatest width being along the hinge-line, 

 which terminates in short, slightly depressed, triangular ears, 

 extending a little beyond the body of the shell : dorsal valve 

 profoundly concave, corresponding very nearly with the curva- 

 ture of the opposite valve : ventral valve ventricose, forming 

 an elevated arch from beak to front, sometimes having a faint 

 depression in the middle from near the umbo to the anterior 

 margin ; umbonal region prominent ; beak incurved, and rising 

 a little above the hinge -line. Surface marked by numerous 

 fine regular striae, which increase both by bifurcation and im- 

 plantation, and are crossed by very fine obscure concentric lines. 



