320 PALAEONTOLOGY OF ILLINOIS. 



If our proposed genus Eriaocrvnus is, as we Lave suspected, identical with 

 Philocrinus of Koninck, the name of this species will have to be written Philo- 

 crinus tuberculatum. 



Locality and position : Upper Coal Measures; Sugar creek, Sangamon county, 

 Illinois, and near Brighton, Jersey county, Illinois. 



MOLLUSCA. 



BRACHIOPODA. 



Genus PRODUCTUS, Sowerby, 1812. 



(Min. Conch., i, p. 153.) 



Productus nanus, M. and W. 



PI. 26, figs. 4a, 4.b, 4c, id. 



Productus nanus, Meek and Worthen, October, 1860. Proceedings Acad. Nat. Sci., 

 Philad., p. 450. 



Shell very small, nearly hemispherical; hinge about equal- 

 ing the greatest breadth; anterior side regularly rounded, sides 

 intersecting the hinge nearly at right angles. Ventral valve 

 gibbous, without any traces of a mesial sinus ; ears triangular, 

 convex and moderately distinct from the swell of the visceral 

 region; umbo ronvex, incurved, and apparently extending 

 slightly beyond the hinge line. Surface ornamented by com- 

 paratively large, rounded, radiating costse, which are rather 

 wider than the grooves between on the convex part of the 

 valve, but suddenly bifurcate, and increase by the intercala- 

 tion of others, around the anterior and antero-lateral margins ; 

 entire surface crossed by numerous very fine concentric striae; 

 visceral region also marked by moderately distinct, rather reg- 

 ular concentric wrinkles, while the bases of a few scattering 

 spines may be seen on the anterior slope. (Dorsal valve 

 unknown.) Length, 0.37 inch; breadth, 0.44 inch; convexity, 

 0.25 inch. 



