52 BRACHIOPODS. 



questionable identity with the typical P. costatus, it seems inad- 

 visable to make any nominal changes until careful and complete 

 comparisons have been instituted. The form appears to be 

 closely related to Martin's P. semireticulatus; and eventually 

 may prove to be merely the young of that species. P. port- 

 lockianus, described by Norwood & Pratten from Carbonaire, is 

 regarded merely as an unimportant local variation of the 

 species. Like all the Carboniferous Product!, this shell has a 

 wide geographical range and quite an extensive distribution in 

 time. 



Productella subalata (HALL). 



Productus subalatus R&U, 1857: 10th Rep. NT. Y. State Mus. Nat. Hist., 



p. 174. 

 Produdus subalatus Hall, 1858 : Geology Iowa, vol. I, p. 500, pi. iii, figs. 



lOa-c. 



Very closely related to and perhaps identical with P. 

 pyxidata. 



Horizon and localities. Devonian, Callaway limestone: 

 Callaway county. 



Productella pyxidata (HALL). 



Plate xxxviii, figs. la-d. 



Productus pyxidatus Hall, 1858: Geology Iowa, vol. I, p. 498, pi. iii, 



figs. 8a-e. 

 Productus shumardianus Hall, 1858: Geology Iowa, vol. I, p. 499, pi. vii, 



fig. 2. 



Shell rather large ( for the genus ), wider than long ; car- 

 dinal extremities rounded ; hinge line usually shorter than 

 greatest width of shell; surface differing from a Productus in 

 being smooth, with concentric often imbricating lines of growth 

 and long spines, few in number. Often low, indistinct radiating 

 ridges are discernible. 



Horizon and localities. Lower Carboniferous, Kinderhook 

 beds : Louisiana, Hannibal, Clarksville ( Pike county). 



