PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 623 
This species is characterized by its large size, attaining about the maximum 
known dimensions for the genus, the wide fold and sulcus, and the subtriangular 
form. It differs from A. australis (Foerste) by its stronger ornamentation, less 
strongly incurved beak, and less tumid brachial valve. 
ANCISTRORHYNCHA CRASSA Cooper, new species 
Plate 99,1, figures 53-61; plate 127, D, figures 20-27; plate 127, I, figures 53-57; 
plate 186, G, figures 26-31 
Shell of about the usual size for the genus, slightly wider than long with 
the greatest width at about the middle. Beak obtuse, posterolateral margins 
short; lateral margins narrowly rounded; anterior margin truncated. Surface 
marked by about 30 rounded costae separated by spaces equal in width to the 
width of the costae. Four or five costae occupy the sulcus, 5 or 6 are on the fold, 
and about 12 on the flanks. 
Pedicle valve moderately convex in lateral profile with the greatest convexity 
at about the middle; beak moderately incurved; sulcus originating about one- 
third the length from the beak, shallow and narrow, occupying less than half the 
width at the front; tongue short and narrowly rounded. Flanks slightly convex 
and with moderate slopes to the margins, Umbonal region and posterior half of 
valve somewhat inflated. 
Brachial valve of about the same depth as the pedicle valve, moderately con- 
vex in lateral profile and with greatest convexity in the umbonal region. An- 
terior profile only moderately convex. Umbo marked by a shallow and narrow 
sulcus for one-third the length from the beak, after which the median fold de- 
velops; fold low, narrow, posteriorly spreading at the front; flanks broad and 
rounded in profile, with moderate slopes. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
Tlofoty pe eee es POI: Pe 8.2 7.5 9.5 5.0 
Paratype (Er 7Bpye wee. 7.0 8.5 7.9 4.6 
Types——Holotype: 111178a; figured paratypes: 111178b; I11184a, 117208a; 
Columbia Univ. 26407(1016) ; unfigured paratypes: 111184b, 117208b. 
Horizon and locahty.—Peery formation in Tennessee: On Clinton (T.V.A. 
137-SW) Quadrangle, 7 miles southwest of Clinton; top of hill north of Elza 
Gate, Oak Ridge, Clinton (T.V.A. 137-SW) Quadrangle. 
Wardell part of Dryen formation in Tennessee: Section 1 mile west of Lone 
Mountain, Tazewell (T.V.A. 154-NE) Quadrangle. 
Ridley formation in Tennessee: On Tennessee Highway 28, 0.6 mile south of 
Chappel Hill Church, 1 mile south of junction with Tennessee Highway 8, Daus 
(T.V.A. 104-SW) Quadrangle. 
Hostler ? formation in Pennsylvania: 1 mile south of Covedale, Blair County. 
Discussion——tThis species differs from all other described ones in the strength 
of the costae covering the surface. In this repect it resembles A. missouriensis, 
but in that species the fold and sulcus are much less well defined than in A. crassa. 
