176 



[ Senate 



Geological position and locality. Shales of the Chemung group 

 Allegany and Chemung counties, New-York. 



Productus hiesutus. 



Productus speciosus (n. s.). 



Pal. N.T. Vol. iv. 



Shell semiglobose, hinge-line less than the greatest width of the 

 shell, extremities rounded or obtusely angular : dorsal valve 

 very regularly concave, flattened somewhat at the hinge ex- 

 tremities, and the ears marked by a few concentric wrinkles; 

 hinge furnished with a small bifurcate dental process : ventral 

 valve ventricose, extremely arcuate, regularly and symme- 

 trically diminishing from the base to the beak, which is 

 incurved beyond the hinge-line; ears not flattened, narrow, 

 scarcely distinct from the body of the shell ; basal margin 

 sinuate, but the €hell without a mesial depression. Surface 

 marked by fine concentric strise and thickly studded with 

 regularly arranged, small, somewhat elongated, spiniferous 

 tubercles. Casts of the shell finely and closely punctate. 

 This species is distinguished from all its associates by the symmetrical 

 form and extremely ventricose chai-acter of the ventral valve, its regular 

 convergence from front to beak and the sinuate basal margin. The spi- 

 niferous tubercles were doubtless furnished with slender, bristle-like 

 spines. 



Geological 'position and locality. Calcareous bands in shaly sandstones 

 of the Chemung group : Chautauque county, N.Y. 



