BRACHIOPODA—PROTREMATA. 



245 



150. P. marginicinctus Prout. Lower Carbonic. 

 Brachial valve subquadrate. A conspicuous marginal fold or 



cincture present on each valve. Surface covered with prominent, 

 rounded, bifurcating costae, the point of bifurcation marked by a 

 spine base. Fine concentric striae cover the entire surface ; these 

 are accompanied on the older portion of the shell by prominent 

 concentric wrinkles. Width about 1 inch ; length somewhat less. 

 St. Louis of Illinois and Missouri. 



151. P.fasciculatus McChesney. Lower Carbonic. 

 Hinge line shorter than width of the shell below. Beak small 



and appressed. Pedicle valve sharply arcuate above and gently 

 curving, with a slight depression. Surface marked with moder- 

 ately fine radiating striae which, when well preserved, have an 

 irregular knotty appearance caused by the thickening of the striae 



Fig. 296. Productus semireticulatus. (Ind. Geol. Surv. ) 



