432 MISSISSIPPIAN BRACHIOPODA 



1883. Spirifera setigera Hall, Rep. N. Y. State Geol. for 1882, pi. (36) 



61, figs. 26-27. 

 1894. Spirifer setigerus Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, pi. 36. 



figs. 26-27. 



1894. Spirifera setigera Keyes, Mo. Geol. Surv., vol. 5, p. 83. 

 1906. Reticularia setigerus Beede, 30th Ann. Rep. Geol. Surv. Ind., p. 1318, 



pi. 21, figs. 1-la. 

 1906. Reticularia pseudolineata ? Beede, 30th Ann. Rep. Geol. Surv. Ind., 



p. 1317, pi. 20, figs. 6-6a ; pi. 21, fig. 5. 

 1911. Reticularia setigera Girty, Bull. U. S. Geol. Survey, No. 439, p. 69, 



pi. 8, fig. 6. 



Description. Shell of medium size or larger, usually a little wider 

 than long, sometimes with the length and breadth nearly equal, sub- 

 elliptical or subcircular in outline, the hinge-line about one-half the width 

 of the shell, the cardinal extremities rounded. The dimensions of a nearly 

 perfect specimen are : length of pedicle valve 24 mm., length of brachial 

 valve 21.3 mm., maximum width 27.5 mm., length of hinge-line 14 mm., 

 thickness 17.5 mm., height of cardinal area 4.4 mm. 



Pedicle valve strongly convex, the greatest convexity posterior to the 

 middle, the surface curving abruptly from the umbo to the cardinal 

 margin, and more gently to the lateral and anterior margins ; mesial sinus 

 originating at the beak or in the umbonal region, shallow or of moderate 

 depth, ill-defined laterally, rounded in the bottom; beak pointed, rather 

 strongly incurved; cardinal area of moderate height, concave with in- 

 creasing curvature towards the beak, not sharply defined at the lateral 

 margins, the surface curving into that of the lateral slopes with only a 

 slight line of differentiation, the surface of the area vertically striate, 

 the lateral margins of the delthyrium bordered by thin, elevated, and 

 somewhat deflected ridges; delthyrium broadly triangular, rather large, 

 open. Internally the hinge-teeth are supported by rather strong dental 

 lamellae which usually diverge anteriorly from the beak at an angle of 

 from 25 to 40 degrees, and extend from one-fourth to one-half of the total 

 length of the valve ; between the dental lamellae is a well-developed 

 median septum which is considerably longer than the lamellae, sometimes 

 reaching to the middle of the valve; the muscular scars are rather 

 narrow, limited laterally by the dental lamella, not deeply impressed, 

 their anterior margins marked by rather indefinite raised ridges which 

 extend obliquely from the anterior extremities of the dentai lamelhe to 

 the extremity of the median septum; in the umbonal region, including 

 the surface of the muscular scars, the inner surface of the valve is marked 

 by radiating costas which rarely reach beyond the middle of the valve. 



Brachial valve less convex than the pedicle, the surface curving 

 abruptly to the cardinal margin from the umbonal region, and more 

 gently to the lateral and anterior margins, sometimes a little compressed 

 towards the cardinal extremities; mesial fold originating at the beak 



