PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 327 
details. For example the ornamentation of Glossorthis consists of strong sub- 
angular costae whereas the ornamentation of Taphrorthis is costellate. Further- 
more Glossorthis is not provided with more than an incipient sulcus in the young. 
In adults the sulcus is completely lost. 
Inside the pedicle valve Glossorthis frequently has a strong lifting of the 
muscle field on a callosity to produce a pseudospondylium. In Taphrorthis this 
tendency, although present, never takes a very tangible form. Inside the brachial 
valve the cardinal process of Taphrorthis never forms the high and thick septum 
that is characteristic of Glossorthis. 
TAPHRORTHIS EMARGINATA Cooper, new species 
Plate 38, A, figures 1, 2; plate 40, A, figures 1-10; plate 49, B, figures 5-10 
Shell subrectangular in outline, attaining a width of about 2 inch; hinge nar- 
rower than the greatest shell width which is at about the middle; cardinal ex- 
tremities obtuse; sides gently rounded; anterolateral extremities narrowly 
rounded ; front margin indented; biconvex, the pedicle valve having the greater 
convexity ; surface multicostellate, costellae unequal in size, appearing in 4 gen- 
erations, I just anterior to the beak, I anterior to the umbo, and 2 between that 
point and the anterior margin; about 10 costellae in 5 mm. at the front margin. 
Pedicle valve moderately convex in lateral profile and with the greatest con- 
vexity in the posterior half; anterior profile moderately convex and with long 
moderately steep slopes ; umbonal region inflated ; shallow sulcus developing an- 
terior to umbo and causing emargination of the front margin; flanks gently 
swollen ; posterolateral extremities small ; umbonal slopes short and steep; inter- 
area curved apsacline ; beak incurved. 
Brachial valve moderately convex in lateral profile and with the maximum 
depth in the posterior half; anterior profile depressed medially but with some- 
what narrowly rounded flanks bounding sulcus and steep, short lateral slopes. 
Sulcus originating at the umbo and extending to the anterior margin where it 
occupies a third the shell width ; posterolateral areas small; umbonal slopes steep. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Fiolotype .fididesias sss: 12.0 10.8 15.0 11.9 6.8 
Paratype (116889c).. 8.9 7.9 12.4 10.4 4.7 
si (116889b).. 8.9 8.2 11.4 ? 4.2 
Types.—Holotype: 116889a; figured paratypes: 117983a,b, 116889b,c; un- 
figured paratypes: 11688qd-f, 116890, 116891a-d. 
Horizon and locality.—Little Oak formation in Alabama: In a cut on U. S. 
Highway 31, 4 mile north of Pelham, Bessemer Iron District (15’) Quadrangle; 
Bailey Gap road junction with Cahaba Valley road SW4SW35 sec. 13, T. 19 S., 
R. 2 W., 1} miles northeast of Newhope Church, Vandiver (15’) Quadrangle. 
Arline formation in Tennessee: 100 yards southwest of the Negro Cemetery, 
4 mile northeast of Friendsville, Concord (T.V.A. 138-SW) Quadrangle. 
Discussion.—See T. peculiarts. 
