480 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Lenoir formation (lower 100 feet) in Tennessee: 14 miles south of Phila- 
delphia, Philadelphia (T.V.A. 131-NW) Quadrangle; # mile northeast of 
Friendsville ; south side of cemetery at Quaker Church, northwest corner Friends- 
ville; Concord (T.V.A. 138-SW) Quadrangle. 
Discussion.—This species hitherto has been referred to in literature on the 
Southern Appalachians as Raymond’s species Hebertella vulgaris, but several 
significant differences may be noted. The Champlain Valley species has a wider 
hinge and the cardinal extremities are much more prominent than those of the 
Tennessee specimens. The southern species is much less regular in outline and 
has a longer interarea, a longer and more curved beak. The costae in both 
species are very regular and direct. In both, intercalations take place only at the 
umbo and the number of costae is about the same. Nevertheless, those of 
M. nuclea are separated by somewhat wider intercostal spaces which give the 
species the appearance of being somewhat coarser ribbed than it is. 
Mimella nucleoidea resembles the southern species, but it has different ribbing 
and had both valves more convex than those of M. nuclea. The latter is a fairly 
common species in the calcarenites associated with the Lenoir formation. It is 
also found in shales particularly around Philadelphia, Tenn. It occurs in cal- 
carenites from Alabama to southern Virginia. 
MIMELLA NUCLEOIDEA Cooper, new species 
Plate 87, B, figures 6-15 
Hebertella vulgaris RayMonD (part), Ann. Carnegie Mus., vol. 7, No. 2, p. 242, text figs. 15, 
17, 18, pl. 36, figs. 2, 4, 5?, I91T. 
Small, wider than long, subrectangular in outline, sides gently rounded and 
anterior margin broadly rounded; greatest width at or anterior to the middle; 
anterior commissure rectimarginate. Hinge narrower than the shell width; cardi- 
nal extremities obtuse, not prominent. Multicostellate, about 9 costellae in 5 mm. 
at the front margin. Costellae narrowly rounded, separated by spaces having a 
width about equal to the width of the costellae. Costellae increasing by intercala- 
tion and bifurcation, particularly at about midlength of the valve; anterior inter- 
calations scattered and usually few. 
Pedicle valve moderately convex in lateral profile, most convex in the posterior 
half, somewhat flattened anteriorly ; broadly and gently convex in anterior pro- 
file; posterior and umbonal region moderately swollen, anterior region broadly 
flattened ; lateral areas gently rounded but with short, steep slopes to the cardinal 
extremities. Beak long, moderately incurved ; interarea long, strongly apsacline. 
Brachial valve in lateral profile evenly and moderately convex with the great- 
est convexity at about the midlength; anterior profile strongly and broadly 
rounded with short, steep lateral slopes; umbonal region swollen; beak strongly 
incurved and overhanging the pedicle interarea; umbo depressed medianly by a 
shallow sulcus that widens slightly anteriorly and extends nearly to the anterior 
margin; sulcus never prominent and often disappearing at the front margin. 
