482 NORTH AMERICAN INDEX FOSSILS. 



10. P. conoideus Hall. (Fig. 1792, d.) Mississippic. 

 Differs from P. elongatus in its smaller and more conical calyx, 



with very short, almost flat base. 



Keokuk of Missouri ; Warsaw of Indiana ; St. Louis of Indiana, 

 Illinois and Missouri. 



11. P. elegans Lyon. Mississippic. 

 Like P. pyriformis in general size and outline but proportionally 



broader. 



Maxville of Ohio and Kentucky? 



12. P. globosus Troost. Mississippic. 

 Calyx very small, globose, with greatest diameter about the 



center. 



Kaskaskia of Illinois, Alabama ( ?) and Tennessee. 



13. P. godoni Def ranee. (Fig. 1793, b.) Mississippic. 

 Differs from P. elongatus in its globose calyx. (Type of genus.) 



Fig. 1793. ^ (left)> Pentremites Fig. 1794. Pentremites cervinus. (After 

 pyriformis ; b, P. godoni. (After Hall, Hall, lowaGeol., I., 2.) 

 Iowa Geol., I.,2. ) 



Kaskaskia of Georgia, Kentucky, Tennessee, Alabama, Indiana, 

 Illinois and Missouri. 



14. P. obesus Lyon. Mississippic. 

 Calyx somewhat globose, and very large and massive ; height 



two or more inches. Differs from P. sulcatus in the greater length 

 of the calyx, especially of the basal portion, the less truncate 

 summit and the somewhat less curved ambulacra. 

 Kaskaskia of Kentucky, Illinois and Missouri. 



15. P. pyriformis Say. (Fig. 1793, a.) Mississippic. 

 Calyx pear-shaped, with greatest diameter in the middle and 



with the summit obtuse and rounded and base narrow, often 

 remaining attached to the upper joint of the column. Height 

 three fourths inch or more. 



