PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 361 
Subfamily GLyptorTHINAE Schuchert and Cooper, 1931 
Specialized Hesperorthidae with interior characters similar to Hesperorthis 
but with an imbricated external surface. Pseudodeltidium and chilidium usually 
absent but small apical (pedicle?) plate present. 
Genus GLYPTORTHIS Foerste, 1914 
Glypthorthis Forrste, Bull. Sci. Lab., Denison Univ., vol. 17, p. 258, 1914..—-SCHUCHERT and 
Cooper, Mem. Peabody Mus. Nat. Hist., vol. 4, pt. 1, p. 89, 1932. 
GLYPTORTHIS ALTA Cooper, new species 
Plate 44, A, figures 1-5 
Shell of moderate size for the genus, hemipyramidal in outline; biconvex; 
valves of unequal depth. Cardinal extremities obtuse. Lateral margins gently 
rounded ; front margin broadly rounded. Anterior commissure faintly uniplicate. 
Surface multicostellate, with 8 costellae occupying a space of 5 mm. at the front. 
Costellae increasing by intercalation. 
Pedicle valve hemipyramidal; unequally convex in lateral profile, with the 
umbonal region moderately convex, the midportion of the profile flat and the 
anterior quarter gently convex. Lateral slopes steep. A narrow, shallow sulcus 
extends from the umbo to the front margin where it forms a slight tongue. In- 
terarea long, nearly flat, strongly apsacline. Delthyrium long and narrow. Den- 
tal plates short, receding ; anterior margin of muscle field thickened. 
Brachial valve moderately convex in both profiles, somewhat swollen and with 
moderately steep lateral slopes. Sulcus present on umbo but obsolete toward 
the front where a narrow fold is barely discernible. Interarea long, deeply con- 
cave, orthocline in position. Cardinalia ponderous; median ridge slender. 
Measurements in mm.—Holotype, length 11.0, brachial length 11.0, width 
13.5, hinge width 11.5, thickness 10.0. 
Type.—Holotype: 110008. 
Horizon and locality—Kimmswick formation in Missouri: Goetz Quarry, 
Jefferson County. 
Discussion.—This species suggests G. obesa in its form and ornamentation, 
but the interarea of the pedicle valve is much longer and more strongly inclined. 
The specimen referred by Bradley (Contr. Walker Mus., Univ. Chicago, vol. 2, 
No. 6, p. 227, pl. 23, figs. 13-15, 1930) to Clitambonites diversus may belong 
to this species. No cardinal view of that specimen is given which would reveal 
the presence or absence of a pseudodeltidium, but the profiles suggest this new 
Glyptorthis. 
GLYPTORTHIS ASSIMILIS Cooper, new species 
Plate 45, C, figures 15-35; plate 40, F, figures 27-32 
Shell of medium to large size for the genus, wider than long in the young but 
with the length and width about equal in adults. Hinge forming the widest part 
in the young, becoming narrower in large specimens. Valves subequal in depth, 
