PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 855 
rina is the irregular wrinkling of the visceral region of both valves and the lack 
of geniculation or the modest development of that feature. Bellimurina is quite 
unlike Leptaena in both respects. In the latter genus wrinkling is usually quite 
uniform, concentric, and strong. Geniculation in that genus, in contrast to this 
feature of Bellimurina, is very strong and often at an angle of about 90°. 
The interior of Bellimurina is most like that of Murinella but lacks the strong 
subperipheral band in the brachial valve as in the latter genus. The median 
ridge extending a short distance anterior to the notothyrial platform of Belli- 
murina is somewhat stronger than that feature in Murinella. 
Bellimurina is generally an uncommon genus and when found is usually identi- 
fied as Leptaena charlottae. The wide identification of this species has misled 
some authors to age assignments and correlations that are unwarranted. This 
genus occurs in the Platteville limestone of the upper Mississippi Valley, but the 
specimens in the National Collection are not suitable for description. In the 
Southern Appalachians the genus is known from the Pratt Ferry limestone up. 
Several species are here described on the basis of pedicle valves only because 
of the fairly distinctive wrinkling of these individuals. The brachial valve is 
usually not as important for description of species of this genus as the pedicle 
valve. 
A few specimens of Bellimurina are known that are as strongly geniculated 
as most of the members of the genus Dactylogonia. These seem to be exceptions. 
Bellimurina is readily distinguished from Dactylogonia by its lack of the strong, 
bladelike adductor plates so characteristic of the latter. 
BELLIMURINA CHARLOTTAE (Winchell and Schuchert), 1892 
Plate 222, G, figures 11-14; plate 223, H, figures 19-24 
Leptaena charlottae WINCHELL and ScHuUcHERT, Amer. Geol., vol. 9, p. 288, Apr. 1, 1892; 
Geol. Minnesota, vol. 3, p. 410, pl. 32, figs. 1-5, 1895.—BAssLER, Cambrian and Ordovi- 
cian: Maryland Geol. Surv., p. 257, pl. 41, figs. 11-13, 1910. 
Strophomena halli, Sarveson, Minnesota Acad. Nat. Sci., Bull. 3, p. 334, pl. 4, figs. 36-38, 
Apr. 9, 1802. 
Types.—Figured hypotypes: Y.P.M. $3619, S3620a,b; U.S.N.M. 45358a. 
Horizon and locality Decorah formation (Rhinidictya bed of the Guttenberg 
member) in Minnesota: At West St. Paul and Minneapolis. 
Discussion.—Some specimens of this species are suggestive of Dactylogonia 
in the form of the pedicle valve and the degree of geniculation. These seem to 
be exceptions, however, and the majority of specimens are not strongly 
geniculated. 
BELLIMURINA COMPRESSA Cooper, new species 
Plate 221, D, figures 23-28 
Shell small, biconvex but with brachial valve having the greater depth; wider 
than long ; widest part at about the middle; sides and anterior margins rounded ; 
surface of visceral region marked by oblique, concentric, irregular wrinkles. 
Alternating costellae cover the entire surface. 
