The I'oiiiia of the Maxrille Li'iiestoiie. 373- 



18GU. Pioductus ccstriciisis. W'ortheii, Trans. St. Louis Acad. Sci.,. 

 Vol. 1, p. 57(1. 

 Chester limestone: C"hester, Illinois. 

 1877. Productus clcgaus. Hall and WhitlRld, U. S. Geol. Expl. 4(i Par.,. 

 Vol. IV, p. 208, pi. r^, ligs. 3, 4. 

 Lower Carboniferous limestone: Utah. 

 18!)L Prodiicfiis clcyans. Whitfield, Ann. X. Y. Acad. Sci., Vol. V, p.^ 

 ■jS], pi. l;-!, Jigs. Lj, lii. 

 Maxville limestone : Ohio. 

 1804. Productus ccstriciisis. Keyes. Mo. Geol. Surv., Vol. V, p. 44. 



Kaskaskia limestone : Ste. Mary, Missouri. 

 1895. Productus clegans. Whitfield, Geol. Surv. Ohio, Vol. VU, p. 4G!),. 

 pi. !l, figs. 15, 1(!. 

 Maxville limestone: Ohio. 

 18!;I7. Proditctus ccstricusis. Weller, Trans. N. Y. Acad. Sci., Vol. X\'T,. 

 p. 256, pi. Ul, figs. 7-'J. 

 Batesville sandstone : 1 Satesville, Arkansas. 

 1911. Diaphragmus clc(/aus. Girty, U. S. Geol. Sur\- , Bull. 430, p. 51,. 

 pi. 4, figs. 4, 5. 

 Moorefield shale: i'.atesville quadrangle, Arkansas 



Description. — Shell of meditim size, highly curved. Hinge- 

 line straight and short. 



Pedicle valve strongly ctirved, gradually increases in breadth 

 from the beak toward the anterior end where it is slightly ex- 

 panded in the older forms. Atiricttlar depressions at the extrem- 

 ities of the hinge line very small. In many specimens a shallow, 

 ill-defined sinus extends from near the beak to the anterior end. 

 Surface marked with numerous, medium-sized, radiating plica- 

 tions which bear a number of spine bases. Plications crossed by 

 concentric wrinkles in the posterior region. 



brachial valve with central portion nearly flat or concave, 

 and with anterior half bending abruptly forward and fitting in- 

 the opposite valve so as to greatly restrict the viseral cavity. 

 Stirface ornamented with medium-sized, radiating plications 

 which are less distinct on the flattened portion and which, in this. 

 area, are crossed by concentric wrinkles. 



Length t6 mm.; width i6 mm. 



This species is characterized b}' the highly curved pedicle 



