1888.] NATURAL SCIENCES OF PHILADELPHIA. 227 



collected are, on the average, smaller than those from other localities. 

 Meek and Worthen regard D. missouriensis Shumard a synonym of 

 this species. 



Productus nanus Meek and Worthen. 



Productus nanus Meek and Worthen, 1860. Proc. Acad. Nat. 

 Sci.' Phila., p. 450. 



Productus nanus Meek and Worthen, 1866. Geol. 111., Vol. II, 

 p. 320, pi. xxvi, figs. 4a, 4b, 4c, 4d. 



This species was described from the lower coal measures of Jeffer- 

 son county, and inasmuch as the St. Louis limestone is exposed in 

 many of the creeks of that locality, its horizon is near the base of 

 the coal measures ; the horizon at Des Moines from which the spec- 

 imens under consideration were obtained is somewhat higher. 

 Though quite rare it will doubtless be found in other localities in 

 the Des Moines valley. It is associated with P. muricatus N. and 

 P. to which it presents differences that are both characteristic and 

 constant. The almost total absence of spines in this species forms a 

 marked contrast with the congeneric species of the same locality. 



Productus cora D'Orbigny. 



Productus cava d'Orbiguy, 1842. Voyage dans I'Amerique 



Meridionale. 

 Productus prattenianus Norwood, 1854. Jour. Acad. Nat. Sci. 



Phila., Vol. Ill, p. 17. 

 Productus cequicostatus Shumard, 1855. Geol. Rep. Missouri, p. 



201, pi. C, fig. 10. 

 Productus flemingi Geinitz, 1866. Carb. und Dyas in Nebraska, 



p. 52, tab. iv, figs. 1, 2, 3, 4. 

 Productus cora White, 1884. Ind. Geol. Kept, for 1883, p. 126, pi. 



xxvi, figs. 1, 2, 3. 

 A single specimen from the Polk County coal mine. This species 

 was originally described from South America ; but with the exception 

 of Owen' and Marcou,^ American paleontologists have until quite 

 recently adopted for this form Norwood's name of P. prattenianus. 

 A Productus collected from the Kinderhook in the vicinity of 

 Burlington, and from the same horizon in Marshall county, unques- 

 tionably belongs to this species ; if, however, this is the form de- 

 scribed by White^ as P. Icevicostus, the latter is certainly synonymous 



^ Geol. Rep. Iowa, Wisconsin and Minnesota, 1852. 



2 Geology of North America, 1858. 



3 Boston Jour. Nat. His., Vol. VII, p. 230, I860. 



