NO. 1395. CAMBRIAN BRA CHIOPODA— WALCOTT. 231 



BILLINGSELLA? APPALACHIA, new species. 



The outline of the dorsal valve is rounded subquadi'ate. The height 

 and width of the venti'al valve are about the same. Dorsal valve 

 slightly transverse. 



The surface is marked by round, very fine, radiating costse, and 

 lines of growth, with very fine interstitial concentric stri^. 



The average size of the ventral valve is about 10 mm. in height 

 with an equal width. The largest shell observed was a ventral valve 

 with a width of 14 mm. 



Cardinal area of the ventral valve rather low. It is divided midway 

 by a rather strong delthyrium. 



Ohservatimis. — This shell in form and size is much like that of Bf 

 anomala. It differs in strongly marked surface characters. All the 

 specimens are flattened in the shale by compression, and nothing is 

 known of the interior characters. 



Formation and locality. — Upper Cambrian. Rogersville shales. 

 Four miles northeast of Rogersville, on roadside just east of Harlan's 

 Knob, Tennessee. 



BILLINGESLLA COLORADOENSIS Shumard. 



OrtMs coloradoensis Shumard, Trans. St. Louis Acad. Sci., I, 1860, p. 627. 

 Orthis pepina Hall, 16th Kept. N. Y. State Cab. Nat. Hist., 1863, p. 134, pi. vi, 



figs. 23-27. 

 Orthis pepina Hall, Trans. Albany Institute, V, 1867, j). 113. 

 Orthis pepina Whitfield, Geol. Wisconsin, IV, 1882, p. 170, pi. i, figs. 4, 5. 

 Orthis f (Orthisinaf) pepina Hall, 2d Ann. Rpt. N. Y. State Geologist, 1883, 



pi. XXXVII, figs. 16-19. 

 BiUingsella pepina Hall and Clarke, Pal. New York, VIII, 1892, Pt. 1, pi. 



VII, figs. 18-19; pi. viiA, figs. 7-9. 

 Orthis (BiUingsella) pepina Sardesox, Bull. Minnesota Acad. Nat. Sci., IV, 



1896, p. 96. 

 BiUingsella coloradoensis Schuchert, Bull. U. S. Geol. Sur., No. 87, 1897, p. 158. 

 BiUingsella coloradoensis Walcott, Mongr. XXXII, U. S. Geol. Survey, Pt. 2, 



1899, p. 450, pi. Lxi, tigs. 1, 1 a-d. 



Shell usually transverse, but in many examples the ventral valve is 

 longer than wide. The general outline is irregularly subquadrate to 

 subsemicircular. On the ventral valve the hinge line slopes toward 

 the beak at a low angle, while in the dorsal valve it is nearly straight. 

 In some individuals the greatest width is at the hinge line. In others 

 it is at about the middle. There is considerable variation in the rela- 

 tive proportions of length and breadth. 



The ventral valve is slightly more convex than the dorsal. The 

 degree of convexity of the two valves varies considerably in specimens 

 from different localities. Some of the ventral valves from the Hudson 

 beds at Franconia, Minnesota and the young shells from Trempealeau, 

 Wisconsin are strongly convex. 



