PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 431 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Hypotype (36101a).......... 18.4 19.4 25.2 22.5 6.3 
ro ESOIGED) aasiceaie «oe 14.7 16.2 22.1 19.3 5.5 
- Peoledver ae. s 1:3 12.8 17.0 18.0 4.4 
Figured hypotype.—36101a; measured hypotypes: 36101b,c. 
Horizon and locality.—Platteville formation (McGregor member) in Wiscon- 
sin: At Highland, Iowa County; Mineral Point, Iowa County; Beloit, Rock 
County ; quarry on Wisconsin Highway 81, 1 mile northwest of Ellenboro, Lan- 
caster (30’) Quadrangle; Rocktown; Gratiot, Lafayette County; Janesville, 
Rock County ; Pomeroy Quarry, River Falls, Pierce County; Dodgeville, Iowa 
County; Argyle, Lafayette County; NE+ sec. 8, T. 3 N., R. 1 W., Platteville 
Township, Grant County ; 0.1 mile south of the Little Platte River on Wisconsin 
Highway 81, 2 miles northwest of Platteville, Lancaster (30’) Quadrangle. 
Same formation in Minnesota: At Minneapolis. 
Same formation in Illinois: At Dixon, 1.5 miles northeast of Dixon; Lee 
County ; 3 miles above Savanna, Jo Daviess County. 
Discussion.—This species has the appearance of a large and robust Valcourea. 
In the young the cardinal extremities are angular and often auriculate. It is 
probably to some young specimens that Conrad gave the name Strophomena recta 
in 1843. Hall’s figures in Paleontology of New York, vol. 1, suggest a young 
form. 
Some variation is apparent in the concavity of the pedicle valve. A few speci- 
mens show a nearly plane pedicle valve, but the majority of them indicate a 
strongly concave pedicle valve and a folded, uniplicate brachial valve. These 
features distinguish C. deflecta from C. subplana. 
CAMPYLORTHIS SUBPLANA Ulrich and Cooper, new species 
Plate 68, B, figures 5-12 
Campylorthis deflecta UtricH and Cooper (not Conrad), Journ. Paleont., vol. 16, No. 5, 
pp. 621, 622, 1942. 
Shell of about usual size for the genus, wider than long; subelliptical to sub- 
rectangular in outline; hinge narrower than the width at the middle in adults 
but forming the widest part in young specimens; cardinal extremities alate in 
the young but narrowly rounded in adults; anterior commissure gently unipli- 
cate ; lateral commissure strongly deflected in the brachial direction at the cardi- 
nal extremities ; surface multicostellate ; costellae broad and with striae narrower 
than the costellae; about 10 to 12 costellae in 5 mm. at the front margin. 
Pedicle valve unevenly convex in lateral profile, the umbonal region slightly 
convex but the remainder gently concave, anterior profile broadly and gently 
concave; umbonal region narrowly convex, the convexity continued to the mid- 
dle as a low fold; anteromedian area depressed into a shallow sulcus; flanks 
gently concave; cardinal extremities strongly and abruptly deflected toward the 
brachial valve ; interarea long, nearly catacline; muscle field rectangular in out- 
