458 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
what swollen anterior slope; lateral areas gently swollen; interior with thick 
notothyrial platform and low median ridge. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Foletyne tat. dcmns <q taser it-> 15.5+ 14.7 19.7 17.2 7.6 
Paratype (117031) 20 .2-+-+.% 12.2 11.5 16.0 12.9 7.0 
Types.—Holotype: 117030; figured paratypes: 117031, 117032a,b. 
Horizon and locality —Ridley formation on the Kensington (T.V.A. 106-SE) 
Quadrangle in Georgia: On U. S. Highway 27 just northwest of Chickamauga 
Creek; quarry on the west side of the road 14 miles south-southeast of Cove 
Church, 5 miles south of Chickamauga. 
Discussion.—This species is characterized by its transversely subrectangular 
outline and strong costellae. It differs from D. regularis in its extended outline 
and wide hinge as well as stronger costellae. It differs from D. winchelli Cooper 
which is also a wide-hinged species in its almost complete lack of a fold and 
sulcus and the rectimarginate anterior commissure. The species was seen only 
in Georgia. 
DOLEROIDES GIBBOSUS (Billings) 
Plate 93, B, figures 8-14 
Orthis gibbosa Brtuincs, Geol. Surv. Canada, Rep. Progress for 1856, p. 296, 1857. 
Doleroides gibbosus (Billings) Coorer, Journ. Paleont., vol. 4, No. 4, p. 375, 382; pl. 35, 
figs. 5-7; pl. 37, fig. 2, 1930.—Wutson, A. E., Geol. Surv. Canada Bull. 8, p. 49, pl. 3, 
figs. 27a, b, 1946. 
Subcircular to subelliptical in outline, lenticular in profile, the brachial valve 
generally having the greater depth; hinge narrower than the greatest shell width 
which is located at or anterior to the middle. Anterior margin broadly rounded, 
lateral margins convex. Anterior commissure more or less strongly uniplicate. 
Surface multicostellate, costellae subequal, 9 in 5 mm. in the sulcus; costellae on 
the flanks alternating in size. 
Pedicle valve moderately convex in lateral profile with the greatest convexity 
located in the posterior half; sulcus originating anterior to the umbo, generally 
wide and shallow but variable, some specimens having a fairly deep and narrow 
sulcus. Flanks gently convex with steep slopes to the cardinal extremities, Inter- 
area moderately long, apsacline. 
Brachial valve evenly and moderately convex with the greatest convexity in 
the median region ; anterior profile broadly convex with the midregion flattened. 
Umbo marked by a shallow and narrow sulcus, usually indistinct ; fold originat- 
ing posterior to the middle, low, flattened, often not distinctly marked from the 
flanks except at the anterior. Flanks gently convex with steep slopes to the 
margins, 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Hypotype (110588a)........ 17.6 16.0 20.8 14.3 10.6 
ff (aaz7aa ys eT. 16.4 15.4 19.3 14.0 10.7 
" CZA774D) ooh eee 18.4 16.6 21.8 13.7 12.9 
