132 MISSISSIPPIAN BRACHIOPODA 



The dimensions of two nearly complete pedicle valves, the first of which 

 is one of the co-types, are : length from hinge-line to front margin 6.3 mm. 

 and 5.5 mm., length from umbonal region to front margin 7.2 mm. and 

 6.5 mm., greatest width 6.9 mm. and 5.5 mm., length of hinge-line 5.6 mm. 

 and 5 mm., convexity 4 mm. and 3.5 mm. 



Pedicle valve strongly convex, the greatest convexity posterior to the 

 middle, the umbonal region broad and prominent, strongly protuberant 

 beyond the hinge-line, the surface rather narrowly rounded transversely 

 along the median line of the valve, curving rather abruptly to the lateral 

 margins and more gently to the anterior margin, a little compressed 

 toward the cardinal extremities, the auricular extensions inconspicuous; 

 mesial sinus obsolete; beak strongly incurved and extending beyond the 

 hinge-line. Surface without regular radiating costae, but marked by fine, 

 concentric lines of growth which are somewhat more prominent at inter- 

 vals, giving a rather indefinite concentrically banded appearance. Spine 

 bases of moderate size with a tendency to be arranged in somewhat irreg- 

 ular concentric rows. 



Brachial valve not observed. 



Remarks. The original illustrations of this species suggest a shell 

 similar to P. biseriatus, but in fact the two species are entirely different. 

 P. indianensis is much smaller than P. biseriatus, narrower, more strongly 

 convex, and with a much more prominent umbonal region in the pedicle 

 valve. The surface markings of the two shells are also very different, 

 the spines of P. indianensis are apparently not the fine, closely appressed 

 spines of P. biseriatus and P. punctatus, but are more erect, and the shell 

 does not exhibit the distinctly banded markings of P. biseriatus. The 

 style of ornamentation with the absence of radiating costse and somewhat 

 indefinitely arranged spine bases suggests some of the shells from the 

 Devonian and lower Mississippian faunas which have usually been re- 

 ferred to the genus Productella, and it is possible that this species should 

 be so referred. 



Horizon. Salem limestone. 



PRODUCTUS OVATUS Hall 

 Plate XVI, Figs, 1-15 



1858. Productus ovatus Hall, Geol. Iowa, vol. 1, pt. 2, p. 674, pi. 24, fig. 1. 



1859. Productus pileiformis McChesney, Desc. New Pal. Foss., p. 40. 

 3860. Productus Icevicostus White, Jour. Boston Soc. Nat. Hist., vol. 7, 



p. 230. 

 1863. Productus corozformis Swallow, Trans. St. Louis Acad. Sci., vol. 2, 



p. 94. 

 1874. Productus prattenianus (= f P. Icevicostus} White, Prelim. Rep. 



Inv. Foss., p. 17. 

 1877. Productus prattenianus (pars.) White, U. S. Geog. Surveys W. 100th 



Mer., vol. 4, p. 113. 



