Maryland Geological Survey 629 



Pteeinea chemungensis (Conrad) 

 Plate LXI, Fig. 23 



Avicula chemungensis Conrad, 1842, Journ. Phila. Acad., voL viii, p. 243. 

 Pterinea chemungensis Hall, 1884, Pal. of N. Y., vol. v, pt. i, p. 98, pi. xvi, 



figs. 3, 7, 10, pi. Ixxxiv, fig. 21. 

 Pterinea chemungensis Grabau and Shimer, 1909, N. Amer. Index Foss., vol. 



i, p. 421, fig. 552. 



Description. — Shell large, obliquely subovate in outline; length less 

 than height, greatest length below the middle. Left valve moderately 

 convex, right valve depressed. Hinge-line straight, nearly equalling the 

 length of the shell. Beak anterior; anterior wing short, nearly equilat- 

 eral, well set off from body of shell; posterior wing large subtriangailar. 

 Surface of left valve marked by slender subequal or alternating rays con- 

 tinuing over the posterior wing; interspaces flat. These are crossed by 

 concentric strige or interrupted by growth varices. 



Length 60 mm.; height 50 mm. 



This is a very characteristic member of the Chemung fauna in New 

 York. 



Williams cites this as one of the dominant species of the Chemung of 

 New York. While abundant in the Chemung of Maryland it is not con- 

 fined to that fauna, but occurs, though rarely, both in the Parkhead and 

 Ithaca. 



Occurrence. — Jennings Formation, Chemung Member. Oakland- 

 Altamont Road; National Road west of Frostburg; EUerslie, Pennsyl- 

 vania, 1316, 1474 abundant, 1508 abundant; AVilliams Road, on Polish 

 Mountain, 2042 ; National Road, on Polish Mountain, 2706, 2929 ; Penn- 

 sylvania state line, west of Green Ridge, upper Tropidolepius zone; 

 Town Creek, 2228; Fifteenmile Creek, 1 mile above Little Orleans, 

 2215 ?; 21/jt miles northeast of Pratt near home of M^r. Cheney. 

 Parkhead Member. Allegany Grove, 850. Woodmont Member, 

 Ithaca Fauna. Little Orleans, 1446; Fifteenmile Creek, 1 mile above 

 Little Orleans, 1446. 



Collection. — Maryland Geological Survey. 



