PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 477 
on U. S. Highway 25W, 4.7 miles south of Clinton, Powell Station (T.V.A. 
137-SE) Quadrangle. 
Discussion—Mimella intermedia is characterized by a subquadrate form, 
nearly rectimarginate anterior commissure, fairly strongly convex valves and 
fairly strong ornamentation. The species resembles M. subquadrata but differs 
in having somewhat finer costellae, more erect and elongate pedicle beak, some- 
what narrower hinge, and less prominently waved anterior commissure. 
This species might be confused with some of the stratigraphically younger nar- 
row forms of M. globosa. The latter are generally thicker shelled and give evi- 
dence of obesity rather than normal specific characters. These obese forms also 
generally have much more swollen valves than the normal Elway and Whistle 
Creek species. 
MIMELLA LATICARDINIA Cooper, new species 
Plate 90, C, figures 21-34 
Shell of about medium size for the genus, slightly wider than long; greatest 
shell width at about the middle; sides broadly rounded, anterior margin broadly 
rounded. Anterior commissure gently uniplicate. Surface costellate, with 9 
costellae occupying a space of 5 mm. at the front margin of a full-grown speci- 
men. Costellae appear in 3 or 4 generations. 
Pedicle valve most convex in the posterior third when viewed in lateral profile ; 
posterior third moderately convex but anterior two-thirds flattened. Umbonal 
region gently convex with erect beak; sulcus originating 10 to 12 mm. anterior 
to the beak, poorly defined in medium-sized shells, more strongly defined in fully 
grown specimens but in any case seldom deep. Posterior half slightly swollen, 
the fullness continued on each side of the median depression to the anterior mar- 
gin; lateral slopes moderately steep. Interarea long, slightly curved, apsacline. 
Brachial valve with the maximum convexity at about the middle in lateral pro- 
file. Anterior profile strongly convex in the middle but lateral slopes only moder- 
ately steep. Umbo marked by a short (6 or 7 mm.), narrow sulcus changing 
anteriorly into a barely perceptible fold. Median region and posterior swollen, 
with steep slopes to the cardinal extremities and lateral margins. Anterior slope 
gentle. Interarea short, curved, apsacline. 
Pedicle interior with small teeth having deep fossettes; dental plates strong, 
bowed outward near the junction with the floor of the valve and continued an- 
teriorly along the margins of the muscle field as a low ridge. Adductor track 
long and wide at the front; diductor impressions narrower than the adductor 
track ; pallial marks not strongly impressed. 
Brachial valve with short brachiophores, moderately strong median ridge, and 
brachiophore supports resting on the floor of the valve; cardinal process slender. 
Measurements in mm— 
Brachial Hinge 
Length length Width width Thickness 
Holotype. ....<«s0.2 ba aes3e.2 «A 19.4 18.0 21.8 18.0 12.7 
Paratype (it0700b)))... - o: . 14.8 14.4 17.0 13.3 9.8 
a RT TOZOOD) ic. 02 585 oe 17.5 16.6 20.6 16.4 11.0 
