PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 769 
Discussion.—This is a small species occurring in fairly hard limestone boulders 
in the Mystic conglomerate. The matrix has defied preparation of pedicle in- 
teriors because the internal details of that valve are only lightly impressed at 
best in other species of Bimuria comparable to this one. No specimens of the 
brachial valve appear in the collection except ones preserving an impression of 
the exterior. It was thus impossible to obtain the brachial interior by burning 
off the shell. 
This species is most like B. immatura but differs in attaining a larger size 
than any yet noted for the Virginia species. The median swelling is narrower 
than that of B. immatura and the flanks thus more depressed. The flanks are 
also somewhat narrower than in the Virginia species. The Quebec species is 
larger than, and different in shape from, B. siphonata from Alabama. 
BIMURIA PARVULA Cooper, new species 
Plate 184, B, figure 4; plate 210, A, figures 1-4 
Small for the genus, wider than long, with the greatest width at about the 
middle; sides gently convex; anterior margin broadly rounded; anterior com- 
missure narrowly sulcate. Width of hinge slightly less than the maximum shell 
width; surface mostly smooth but anterior half of some specimens showing 
traces of thin lamellae. 
Pedicle valve strongly convex in lateral profile and with a swollen umbo 
which is the most convex part; anterior profile broadly and strongly convex 
with moderately long and steep lateral slopes. Median region swollen; anterior 
slope long and moderately sloping; posterior slope narrowly rounded; beak visi- 
ble only from the brachial side, foramen small in the adult, produced into a short, 
narrow tube in the young adult and immature shell. Interior with wide, short 
teeth ; muscle area not discernible. Interarea short, anacline. 
Brachial valve deeply concave, the maximum concavity located just posterior 
to the middle ; lateral regions less shallow than the median region ; posterolateral 
areas somewhat flattened. Interior with widely divergent brachial process; 
median septum highest in the posterior third or quarter; lateral septa strongly 
elevated and with thick callosities on the side away from the middle. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
Holotype stare eaeee es ee 3.6 7:2 6.1 1.5 2.3 
Paratype (117469a)..... 7.0 ? 8.8 6.8 ? 2.8 
s (117469b)..... 6.1 4.9 a7 6.6 1.5 2.5 
Types.—Holotype: 117469d; figured paratypes: 117469e,f, 123253a; un- 
figured paratypes: 117469a-c. 
Horizon and locality—Chatham Hill formation in Virginia: On northwest 
slope of Walker Mountain, 1.2 miles S. 31° E. of Sharon Springs, Burkes 
Garden (15’) Quadrangle. 
Edinburg limestone (Cyrtonotella zone) in Virginia: On the south side of 
