102 MISSISSIPPIAN BRACHIOPODA 



convexity 7 mm. The dimensions of a brachial valve are; length 21 mm., 

 width 25 mm., length of hinge-line 16 mm. 



Pedicle valve depressed convex, with the greatest convexity near or 

 posterior to the middle, the surface curving with a gently convex curva- 

 ture to the lateral and anterior margins and somewhat compressed to- 

 wards the cardinal extremities, the curvature from the umbonal region 

 to the cardinal margin on each side of the beak rather abrupt, the um- 

 bonal region only very slightly produced posteriorly beyond the hinge- 

 line ; mesial sinus obsolete ; beak small and incurved. 



Brachial valve nearly flat, with a shallow, narrow concavity at the 

 beak whose lateral margins diverge rapidly anteriorly und become less 

 well defined; mesial fold obsolete. Internally the cardinal process is 

 small and bifid, lying in the plane of the valve and projecting beyond 

 the hinge-line into the umbonal cavity of the opposite valve; a low 

 median ridge extends from the base of the cardinal process nearly to the 

 middle of the valve. 



The surface of the pedicle valve is covered by innumerable, fine and 

 delicate spines which attain a length of 5 mm. or more ; the brachial valve 

 is marked throughout by small crowded pits which may represent the 

 position of similar fine spines, although the spines themselves have not 

 been observed; both valves marked by conspicuous and nearly regular, 

 concentric lines of growth. 



Remarks. In the condition of preservation in which this species occurs, 

 in a fine, yellow sandstone of the Kinderhook, the fine surface spines are 

 rarely discernable, but the surface of the pedicle valve possesses a finely 

 granular texture which is more or less conspicuous ; the most conspicuous, 

 surface markings are the very regular concentric lines of growth. The 

 species is characterized by its subcircular outline, being truncated on the 

 posterior side by the hinge-line; by the depressed-convex pedicle valve 

 and the nearly flat brachial valve. The species resembles P. pyxidata 

 but it attains a larger size, with relatively shorter hinge-line and with 

 very different surface markings ; the brachial valve is also much flatter. 



Horizon. Chonopectus sandstone of the Kinderhook. 



PKODUCTELLA SUBL^VIS n. sp. 

 Plate LXXXIII, Figs. 18-20 



Description. Shell large, depressed concavo-convex, wider than long, 

 the hinge-line a little shorter than the greatest width of the shell, lateral 

 and anterior margins describing a regular, subelliptical curve, one side 

 of the ellipse, that on the posterior side of the shell, being incom- 

 plete. The dimensions of the best preserved brachial valve observed, 

 a small individual, are : length 25 mm., width 33 mm., convexity 8 mm., 



