216 Systematic Paleontology — Middle Devonian 



sliglit constriction behind it, angi'lav umbonal ridge and pointed posterior 

 end. 



Length, 23 mm.; height, 6 mm. 



Occurrence. — Eomnky Foemation, Hamilton Member. McCoys 

 Ferry; southwest of McCoys Ferri^; west of Lock No. 56 at Great 

 Cacapon ; W. Va. side Potomac Eiver about 3 miles south of Cumberland. 



Collections. — Maryland Geological Survey; New York State Museum; 

 American Museum of Natural History. 



Genus ORTHONOTA Conrad 



Okthonota undulata Conrad 

 Plate XXI, Figs. 11-13 



Orthonota undulata Conrad, 1841, Geol. Surv. N. Y., An. Rep., p. 51, fig. 6. 

 Orthonota undulata Vanuxem, 1842, Geol. N. Y., pt. iii, p. 150, fig. 2. 

 Orthonota undulata Rogers, 1858, GeoL Penna., vol. ii, pt. ii, p. 827, fig. 661. 

 Orthonota undulata Hall, 1870, Prelim. Notice Lamellibranchiata 2, p. 87. 

 Orthonota undulata Hall, 1885, Pal. N. Y., vol. v, pt. 1, Lamellibranchiata ii, 



p. 478, pi. Ixxviii, figs. 37-42. 

 Orthonota undulata Clarke, 1903, N. Y. State Mus., Bull. 65, p. 469. 

 Orthonota undulata Grabau and Shimer, 1909, N. Am. Index Fossils, vol. i, 



p. 378, fig. 480. 



Description. — " Shell large, extremely elongate, with parallel dorsal 

 and ventral margins; length three times the greatest height; basal margin 

 nearly straight ; slightly constricted anterior to the middle ; posterior end 

 somewhat vertically truncated ; anterior end short, extending for a little 

 distance along the hinge-line and abruptly rounded ; cardinal line straight, 

 extending for about three-fourths the length of the shell. "Valves of 

 moderate convexity ; beaks subanterior small, low, scarcely elevated above 

 the hinge-line; cincture narrow, distinct, extending from the beak to the 

 basal margin, which is sometimes gently constricted; umbonal ridge 

 prominent, rounded, limited below by a narrow furrow, and extending to 

 the post-inferior extremity; cardinal slope wide, marked by a distinct fold 

 along the middle of its length. Surface marked by fine concentric striae, 

 which are in some parts crowded and fasciculate on the body of the shell ; 

 marked by distinct undulations upon the anterior end and post-cardinal 

 slope." Hall, 1S85. 



