384 REPORT ON THE STATE CABINET. 



GENUS AVICULA, Klein. 



AviCULA UNDATA. 

 jivicula undata, Hall. Paleontology of New York, II, p. 283, Plate lix, fig. 2. 



A specimen from Racine, Wisconsin, and another from BridgejDort, 

 Illinois, resemble this species from the Niagara group of New Yorlv. 



AviCULA EMACERATA, CoNRAD. 



jimcula emaceraia, Conrad; in Jour. Acad. Nat. Sci. Phila., VIII, p. 241, Plate xii, fig. 15. 

 Hall. Geol. Report Fourth District N. Y., p. 109. 

 Hall. Pal. N. Y., II, pp. 83, 282, Plate lix, fig. la-e. 



This species occurs at Racine, Wisconsin, and at Bridgeport, Illinois. 

 GENUS PTERINEA, Goldfuss. 



PtERINEA ERISA, N. S. 

 PLATE XIV, FIG. 1. 

 Compare Pterinea stricBcosta, McChesnet. New Palasozoic Fossils. 



Body of the shell obliquely subovate, extremely inequilateral; anterior 

 wing rather long, distinctly sinuate at its junction with the body of 

 the shell, posterior wing short, not extending so far as the posterior 

 extremity of the shell ; umbo prominent, rising a little above the 

 hinge-line. Muscular impression large and nearly round, situated 

 near the middle of the length of the shell. In the cast, beneath 

 the beak or just anterior to it, there is one short curving dental pit, 

 with a smaller accessory one separated by a callosity. The surface 

 of the shell is marked by strong radiating and concentric striae, 

 which, on the partial decomposition of the shell, present a cancella- 

 ted texture resembling that of a bryozoan. 



In one specimen measured, the width from the two extremities along 

 the hinge-line is nine-tenths of an inch; and from the umbo to the pos- 

 tero-basal margin, in the direction of the umbonal slope, it has the same 

 extent ; the length vertically from the hinge-line is six-tenths of an inch. 



Formation and Locality. — At Bridgeport, Illinois. 



