674 GEOLOGICAL SURVEY OF IOWA. 



BRACHIOPODA OF THE ST. LOUIS LIMESTONE. 

 Productus ovatns ( n. s.)- 



PLATE XXIV. Fia.l. 



VENTRAL valve ovoid, rounded below and gradually dimi- 

 nishing, from the broader part of the shell, with a curved 

 outline to the beak, prominently convex in the middle, with 

 the beak incurved : extent of the cardinal extremities un- 

 known. 



SURFACE marked by fine, scarcely elevated, rounded costaB; 

 the cardinal extremities, sides and front of the shell orna- 

 mented by numerous slender elongated tubular spines. 



This species differs from any described one with which I am acquainted. In some 

 of its characters it resembles the P. altonensis ; but the costae are stronger, the shell 

 is less arcuate, and narrower towards the beak. 



Fig. 1. Ventral valve of a specimen of this species. 



Geological position and localities. In the St. Louis limestone : Ottumwa 

 and Keosauqua, Iowa ; and St. Louis, Missouri. 



Productus niargiiiicinctus. 



PLATE XXIV. FIG. 3 a, b, c. 



P roductus marginicinctus : PHOUT, Transactions of the Academy of Sciences of St. Louis, 



Vol. 1, pa. 43, pi. 2, f. 1 - 16. 



SHELL of medium size, subquadrate, usually wider than 

 long. Dorsal valve subquadrate, convex at the beak and 

 depressed on each side, flattened in the middle and towards 

 the base. Ventral valve highly arched with the summit of 

 the arch nearer the beak, broad and gibbous below, narrowing 

 towards the beak, with the sides nearly straight above the 

 middle of the shell : beak closely incurved, and projecting 

 slightly beyond the hinge-line. 



