BART yo CHAZYAN AND RELATED BRACHIOPODS—COOPER 945 
STROPHOMENA PLATTINENSIS Fenton 
Strophomena plattinensis Fenton, Amer. Midland Nat., vol. 11, Nos. 3, 4, p. 149, pl. Io, 
figs. 7-9, 1928. 
Type—Holotype: Walker Mus. 25988; paratypes: Walker Mus. 25501, 
25983. 
Horizon and locality—Platteville formation in Wisconsin: At Mineral Point, 
Mineral Point (30’) Quadrangle. 
Plattin group (Macy formation) in Missouri: South Beckett Hill, Wein- 
garten (15’) Quadrangle. 
STROPHOMENA PLATTINENSIS CRASSA Raasch 
Strophomena plattinensis crassa Raasch, in SHrock and RaascH, Amer. Midland Nat., 
vol. 18, No. 4, pp. 549, 592, pl. 4, figs. 3, 7, 1937. 
Horizon and locality.—Platteville formation (blue beds) in Wisconsin: At 
Beloit, Rock County; 2 miles west of Klevenville, Dane County. 
STROPHOMENA PLATYUMBONA Cooper, new species 
Plate 254, C, figures 7-10 
Shell moderately large for the genus, wider than long and with the greatest 
width at the hinge. Cardinal extremities acute and subauriculate. Sides gently 
rounded and slightly oblique toward the middle; anterior margin somewhat 
narrowly rounded. Surface finely costellate, costellae subequal in size and 
numbering 3 to the millimeter at the front margin. 
Pedicle valve fairly evenly concave in lateral profile and with the deepest part 
located just anterior to the middle; umbo only slightly swollen and the swelling 
continued anteriorly for a short distance only; median region flattened; sides 
and anterior abruptly bent in the direction of the pedicle valve to form a deeply 
concave region just anterior to the middle; cardinal extremities flattened and 
deflected in the direction of the brachial valve. Interior with narrowly elongated 
muscle field and with the diductor scars considerably elongated at their antero- 
median extremities. 
Brachial valve with the posterior third gently concave, the median third mod- 
erately swollen and the anterior third gently convex in lateral profile. Anterior 
profile moderately and broadly convex. Lateral slopes moderately long, mod- 
erately steep; anterior slope somewhat steeper than the lateral ones. Interior 
with short median ridge, short brachiophores, and small cardinal process. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
Holotype” (424.4... dv2pi0 y 30.0 35.9 ? ? 
Paratype (117743b).. 29.8 G 33.5 35.3 ? ? 
= (117743e).. 20.2 28.0 32.4 Fi 4.9 7.0 
Types.—Holotype: 117743a; figured paratypes: 117743b-d; measured para- 
type 117743¢. 
