146 M1SSISS1PPIAN BRACHIOPODA 



tremities, where it is compressed; cardinal area broadly triangular, 

 the cardinal margins sharply angular and nearly straight or gently 

 convex from the beak to the cardinal extremities, its surface nearly 

 flat and lying nearly in the plane of the valve; the delthyrium small, 

 partially closed by the deltidium, which may be incomplete in the speci- 

 men observed. The surface covered with appressed spines of moderate 

 size whose bases occur at intervals of about 2 mm. and tend to be 

 arranged in radiating series, inconspicuous or absent from the umbonal 

 region ; surface marked also by inconspicuous concentric lines of growth. 



Brachial valve concave, its curvature following somewhat closely that 

 of the opposite valve, deflected towards the cardinal extremities ; the beak 

 inconspicuous; the cardinal area much narrower than that of the op- 

 posite valve; the surface marked by more or less irregular, concentric 

 lines of growth with no spine bases. 



Remarks. This species, figured but not described by Hall and Clarke, 

 is the largest which has been recognized in our Mississippian faunas. 

 It resemibles S. beecheri, but is larger, with more conspicuous spine bases 

 upon the pedicle valve. 



Horizon. Kinderhook (New Providence shale, Kentucky). 



STROPHALOSIA BEECHERI Rowley 

 Plate XIX, Figs. 37-38 



1893. Strophalosia beecheri Rowley, Am. Geol., vol. 12, p. 308, pi. 14, 



figs. 18-19. 

 1908. Strophalosia, beecheri Rowley, Mo. Bureau Geol. and Mines, vol. 8, 



2nd ser., p. 76, pi. 17, figs. 24-25. 



Description. Shell unsymmetrical, below medium size, not attached in 

 the mature condition, broader than long, the hinge-line less than the 

 greatest width, the cardinal extremities obtusely angular. The dimen- 

 sions of the holotype, a pedicle, valve, are: length 13.2 mm., greatest 

 width 14.8 mm., length of hinge-line 11 mm., convexity 6 mm. 



Pedicle valve most convex near the middle, the surface sloping with a 

 gently convex curvature to the beak, to the antero-lateral and anterior 

 margins, compressed towards the cardinal extremities, the umbonal region 

 projecting slightly beyond the cardinal margin, the cicatrix small and 

 inconspicuous; cardinal area rather narrow and nearly flat, lying in 

 nearly the plane of the valve, the delthyrium small, closed by a convex 

 deltidium. Surface marked by irregular, concentric lines of growth, and 

 by rather strong spine bases which seem to be arranged in rather irregu- 

 lar concentric lines, the distances between the spines being about 2 mm. 

 or somewhat less, the spines themselves have been destroyed but judging 

 from the position of the bases they must have been nearly erect. 



Brachial valv not known. 



