PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 621 
ANCISTRORHYNCHA COSTATA Ulrich and Cooper 
Plate 126, B, figures 6-9; plate 127, H, figures 47-52; plate 127, J, figures 58-62; plate 120, A, 
figure 1; plate 129, B, figure 2; plate 129, C, figures 3-8; plate 129, D, figures 9-13; 
plate 129, E, figures 14-19; plate 129, F, figures 20-25; plate 129, H, figures 33-38 
Ancistrorhyncha costata Utricu and Cooper, Journ. Paleont., vol. 16, No. 5, p. 625, pl. 90, 
figs. 25-27, 30, 31, 1942. 
Shell small, valves subequal in depth, subtriangular to subpentagonal in out- 
line ; beak slightly greater than a right angle; sides diverging and straight from 
beak to about the middle where the shell attains its maximum width, sides 
rounded at middle; front margin truncated. Surface marked by low, rounded 
costae separated by spaces narrower than the costae. The sulcus is marked by 
6 to 10 costae, the fold by 7 to 11 costae, and the flanks bear about 13 ribs. 
Pedicle valve moderately convex in lateral profile with the greatest convexity 
located in the tumid posterior half. Sulcus originating at about the middle, shal- 
low, with a short, narrowly rounded tongue; sulcus occupying as much as half 
the width at the front. Flanks fairly strongly rounded and with moderately steep 
slopes. 
Brachial valve moderately convex in lateral profile and with the maximum 
curvature at about the middle; anterior profile fairly strongly rounded. Umbo- 
nal and median regions swollen; fold originating slightly anterior to the middle, 
low in most specimens and in some scarcely distinguishable. Flanks moderately 
rounded and with moderately steep slopes. 
Interior: Dental plates strong, separated from inner wall of valve by umbonal 
cavities ; crura long and slender. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
Bioletype? SS OH 7.8 6.7 8.6 5.0 
Hypotype (117204b)............... 8.5 Vey | 10.0 6:0 1% 
* CERO G A ton As 3 riders tee 9.0 8.0 10.0 6.5 
< Ag Te eer eae ie 7.4 6.8 7.7 4.4 
Ke adhe 7) Cian ice v pe 6.5 77. 4.9 
2 RIDETOO) Steed eee 6.9 6.6 7.6 4.8 
? ChI7200d) et. 29S. todd 8.0 7.4 8.9 z 
5 (TI72OGH eC ds ti). idapya ais 6.6 5.0 7 i 3.8 
Types.—Holotype: 108203 ; paratypes: 108204a-l ; 111183; figured hypotypes: 
II119Q6, 117204a,b,c, 117205, 117206b,c, 117207, 123291a, Columbia Univ. 
25880(2120) ; measured hypotypes: 117206a,f. 
Horizon and locality —Ridley or Murfreesboro formation in Sequatchie Val- 
ley, Tenn.: 14 miles southeast of Hembree Mill, Pikesville (15’) Special Quad- 
rangle; Crystal Creek, 5 miles south of Pikeville; Sequatchie Valley ; Murfrees- 
boro; Ridley formation: 0.6 mile south of Chappel Hill Methodist Church on 
Tennessee Highway 28, 1 mile south of its junction with Tennessee Highway 8. 
Same formation in Rutherford County, Tenn.: Stone River bridge on Ten- 
nessee Highway 96, 1 mile west of Murfreesboro; east side of Marshall Knobs 
about 5 miles south of Murfreesboro. 
