130 MISSISSIPPIAN BRACHIOPODA 



margin 10 mm., greatest width 9 mm., length of hinge-line 7.5 mm., con- 

 vexity of pedicle valve 4.5 mm., depth of visceral cavity between the two 

 valves 1.6 mm. 



Pedicle valve strongly convex with the umbonal region prominent and 

 projecting notably beyond the hinge-line, arched longitudinally with the 

 posterior curvature a little shorter and more abrupt than the anterior, 

 the lateral slopes curving more or less gently from the rather narrowly 

 rounded median portion of the valve to the lateral margins, the surface 

 curving abruptly to the cardinal margin, cardinal auriculations small 

 and inconspicuous or obsolete ; mesial sinus obsolete ; beak small, pointed, 

 and strongly incurved beyond the hinge-line. Surface of the valve 

 marked by depressed, rounded, radiating costae which are broader than the 

 intercostal furrows, from one and one-half to three of which occupy the 

 space of one millimeter, the costas increase by bifurcation throughout the 

 entire length of the valve but the divisions are more frequent posteriorly ; 

 crossing the radiating costae are more or less irregular, appressed, concen- 

 tric lamina? which in some conditions of preservation of the shell are very 

 conspicuous. Spine bases few and inconspicuous, sometimes apparently 

 obsolete, when present they are usually confined to about two or three 

 upon each side of the beak arranged in an oblique row from the hinge- 

 line on each side of the beak towards a point on the lateral margin in 

 front of the cardinal extremity. 



Brachial valve deeply concave, closely following the curvature of the 

 pedicle valve, not differentiated into a visceral and a produced portion, 

 the surface slightly deflected towards the cardinal extremities. Surface 

 marked by radiating costae similar to those of the opposite valve, and 

 also by similar concentric laminae. 



Remarks. This small species is entirely different from any other mem- 

 ber of the genus in our faunas. It resembles in a somewhat remote de- 

 gree the Productella halliana of the Lime Creek Devonian fauna of Iowa, 

 but it is commonly a narrower shell, more prominent along the median 

 line of the pedicle valve and with similar markings upon the two valves. 



Horizon. Chouteau limestone, and Fern Glen formation. 



PRODUCTUS CURTIROSTRIS Winchell 

 Plate XIV, Figs. 8-13 



1865. Producta curtirostra Winchell, Proc. Acad. Nat. Sci. Phil., p. 114. 

 1900. Productus semireticulatus Weller, Trans. St. Louis Acad. Sci., vol. 

 10, p. 70, pi. 1, figs. 7-8. 



Description. Shell semielliptical or subsemielliptical in outline, of about 

 medium size or a little larger, length and breadth subequal, the hinge- 

 line equal to or a little shorter than the greatest width. The dimensions 

 of two nearly complete pedicle valves, co-types, are : length from hinge- 

 line to anterior margin 24.5 mm. and 25.2 mm., length from umbonal re- 



