258 Systematic Paleontology — Middle Devonian 



center of cardinal margin; vimbonal slope angular, continuing to post- 

 inferior margin; postcardinal slope concave. Anterior and posterior 

 extremities gaping. Surface ornamented by radial plications, which are 

 about 1 mm. apart upon middle and anterior parts of shell 25 mm. long. 

 Plications become obsolete near anterior extremit}'. They are duplicated 

 and much closer upon postcardinal surface, where they are crossed by 

 conspicuous fine concentric stria?. The middle and anterior part of shell 

 is also crossed by lamellose lines of growth. 



Length 20 mm.; height 20 mm. 



This species closely resembles C cuncus var. nasutum but differs in the 

 much more abrupt constriction of its anterior end. The specimens ob- 

 served are internal casts. 



Occurrence. — Eomney Formation, Hamilton Member. Little Eun, 

 east of Hancock; Williams Eoad, 3^2 miles southeast of Cumberland. 



Collection. — Maryland Geological Survey. 



[C. K. Swartz.] 



Family PTERIIDAE 



Genus ACTINOPTERIA Hall 

 ACTINOPTERIA DECUSSATA Hall 



Plate XXX, Figs. 5-8 



Avicula dcciissata Hall. 1843, Geol. N. Y., pt. iv, p. 203, flgs. 1, 2. 



Actinopteria decussata Hall, 1884, Pal. N. Y., vol. v, pt. i, Lamellibranchiata 



i, p. Ill, pi. xvii, figs. 24, 28; pL xviii, flgs. 1-15; pi. xx, fig. 19; pi. Ixxxiv, 



fig. 4. 

 Actinopteria decussata Keyes, 1891, Johns Hopkins Univ. Circ, vol. xi, p. 29. 

 Actinopteria decussata Clarke, 1903, N. Y. State Mus., Bull. 65, p. 351. 

 Actinopteria decussata Graban and Shimer, 1909, N. Am. Index Fossils, vol. i, 



p. 449. fig. 591c. 



Description. — Shell large, subrhomboidal ; body subovate, very oblique ; 

 length about one-fourth greater than the height ; margins regularly curv- 

 ing, the anterior sometimes nearly vertical, the posterior more abruptly 

 rounded. Valves convex, the right valve less convex and smaller than the 

 left one; hinge-line straight, less than the length of the valve; beak 

 acute, prominent, inclined forward, close to the anterior end of the shell ; 



