180 [Senath 



Productus newberryi (n.s.)- 



Shell semielliptical in outline, somewhat contracted at the cardi- 

 nal extremities : dorsal valve moderately concave, a little more 

 depressed just below the beak ; surface marked by fine closely 

 arranged concentric striae and numerous spiniferous ridges ar- 

 ranged in radiating lines, which are sometimes continuous on 

 the lower half of the valve : ventral valve regularly convex, 

 gibbous, not strongly arched; beak small, projecting little be- 

 yond the hinge-line ; surface marked as in the dorsal valve. 

 This shell reaches the dimensions of one and a half to two inches in 

 width, with a height about two-thirds as great. It approaches in character 

 the P. lachrTjmosa of Conrad, but is a larger shell, with more closely 

 arranged spiniferous ridges, and more contracted hinge extremities as well 

 as other differences. 



Geological positio7i and locality. In shaly sandstone and calcareous 

 sandstone of the age of the Chemung group : Medina county, Ohio. 



Productus concentricus. 



Iowa Geological Report, 1857. 



Shell small, semielliptical in outline : dorsal valve deeply con- 

 cave, sometimes almost geniculate in front ; hinge extremities 

 slightly contracted ; upper half of surface marked by strong 

 concentric wrinkles, and somewhat distant spiniferous tuber- 

 cles : ventral valve unknown. 



This species is distinguished by the strong concentric wrinkles which 

 mark the upper part of the shell. The spiniferous ridges are not unlike 

 those of P. spinulicosta of the Hamilton group, but they are stronger and 

 somewhat more distant. The deeply concave character of the dorsal valve, 

 and consequent gibbosity of the ventral valve, are characters differing from 

 all the others with this form and surface marking. 



Geological position and locality. In the argillaceous sandstone of the 

 age of the Chemung group : Burlington, Iowa. ♦ 



TO BE CONTINUED, 



[ The continuation of this paper will be given in the succeeding Report of the 

 Regents of the University upon the State Collections of Natural History for 

 1857.] 



