BRACHIOPODA. 195 



Genus Wilsonia Kayser 



Wilsonia wadei Dunbar 



Plate 49, figures 35-48; plate 50, figures 1-4 



Wilsonia wadei Dunbar, 1919, Tenn. Geol. Surv., Bull. 21, pi. 2, fig. 8. 



Wilsonia wadei Dunbar, 1920, Trans. Conn. Acad. Arts and Sciences, vol. 23, p. 133, pi. 



Ill, figs. 3, 4. 



Description — "Shell small, subglobular or subpentahedral in form; deepest and 

 strongly truncate at the front margin; length, breadth and height about equal. Ventral 

 valve depressed convex, but sharply deflected, almost angulated along the margins; 

 beak short and small, neatly incurved. A mesial sinus begins about the middle of the 

 valve and is produced anteriorly into a narrow linguiform extension that is sharply 

 deflected at right angles to the plane of the valve. Dorsal valve about as deep as the 

 ventral, also gently convex and steeply angulated at the margins. A fold on the anterior 

 portion corresponds to the sinus of the opposite valve. The surface bears low rounded 

 plications, of which one occupies the sinus, two the fold, and three each lateral slope. 

 Rarely in large specimens there are two plications on the sinus and three on the fold. 

 The plications become obsolescent near the beak. 



"Internally the hinge plate in the dorsal valve bears a crural cavity as in Cama- 

 rotoechia, and the cardinal process is wanting. 



"Dimensions — Length, 9 mm. ; width, 9 mm. ; height, 8.5 mm. Of a large specimen : 

 11 mm., 10.5 mm. and 9.2 mm., respectively." — Dunbar, 1920. 



Remarks — The Missouri representatives have from about 4 to about 7 plications 

 on each lateral slope of each valve, 2 or 3 plications on the fold, and 1 or 2 in the sinus. 



Genus Rhynchonella Fischer 



Rhynchonella transversa Hall 

 Plate 50, figures 5-20 



Rhynchonella transversa Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 



74, figs. 5, 6. 

 Rhynchonella transversa Hall, 1859, Pal. N. Y., vol. Ill, p. 234, pi. XXXIV, figs. 9-16, 



1861. 

 Rhynchonella transversa Weller, 1903, Pal. N. J., vol. Ill, p. 283, pi. XXIX, figs. 28-31. 



Description — "Shell subtriangular, wider than long, tapering abruptly to the 

 beak. Ventral valve depressed convex, most prominent near the beak; beak arched. 

 Dorsal valve a little larger, most elevated near the front; beak incurved; foramen 

 narrow, continued up to the apex of the beak. Surface ornamented by about fourteen 

 or fifteen sharply elevated plications on each valve, of which from three to four are 

 elevated near the front into a rather faint mesial fold, and two or three depressed on 

 the ventral valve so as to form a faint sinus in the front. Somewhat strong zigzag lines 

 of growth mark the surface of the valves near the margin in front." — Hall, 1859. 



Remarks — The specimens at hand have from 12 to 17 plications on each valve, from 

 3 to 4 on the fold, and from 2 to 3 in the sinus. 



Rhynchonella (?) bialveata Hall 

 Plate 50, figures 21-24 



Rhynchonella? bialveata Hall, 1857, 10th Ann. Rept. N.Y. State Cab. Nat. Hist., p. 73. 

 Rhynchonella ? bialveata Hall, 1859, Pal. N. Y., vol. Ill, p. 233, pi. XXXIV, figs. 1-4, 



1861. 

 Rhynchonella bialveata Schuchert, 1897, U. S. Geol. Surv., Bull. 87, p. 355. 



