372 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Types.—Holotype: 116938b; figured paratypes: 116938a,c,e; unfigured para- 
type: 116938d. 
Horizon and locality —Ridley formation in Georgia: On U. S. Highway 27 
just north of Chickamauga Creek, Kensington (T.V.A. 106-SE) Quadrangle. 
Discussion—This species is characterized by its rectangular outline and fairly 
strongly convex brachial valve. It is very suggestive of G. virginica but differs 
in having finer ornamentation, a pedicle valve not flattened in the anteromedian 
portion, a more convex brachial valve, and a less pronounced brachial sulcus. 
GLYPTORTHIS OBESA Cooper, new species 
Plate 47, B, figures 9-12 
Shell of medium size for the genus, strongly biconvex with the length and 
width subequal. Lateral margins gently rounded to nearly straight ; anterior mar- 
gin strongly rounded. Anterior commissure rectimarginate. Surface multicostel- 
late, about 7 costellae occupying the space of 5 mm. at the front margin. 
Pedicle valve subhemipyramidal in outline; lateral profile moderately convex 
with the greatest convexity located in the posterior half. Anterior profile strongly 
convex. Valve strongly swollen in the midregion, with steep lateral slopes. 
Slopes to cardinal extremities gently convex. Interarea long, strongly apsacline. 
Brachial valve wider than long, strongly convex in both profiles and with the 
greatest convexity located at the middle. Midregion swollen. Anterior and 
lateral slopes steep. Slopes to cardinal extremities gently concave. Median sulcus 
defined at the posterior only, obsolete at the front margin of an adult. Interarea 
long, orthocline. 
Interior with heavy and swollen structures. Pedicle muscle field narrow, 
thickened at the front and with an elevated adductor track. Ovarian fields large 
and occupying most of the lateral areas of the interior. Cardinalia of the brachial 
valve ponderous. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype (pedicle valve) ........ 14.6 ? 14.2 12.3 5.3 
Paratype (brachial valve 110068c). 11.7 15.2 ? ? ? 
Types.—Holotype: 110068d; figured paratypes: 110068a,c; unfigured para- 
types: 110068b,e-g. 
Horizon and locality.—Bromide formation (Mountain Lake member) in Okla- 
homa: A little north of the middle of sec. 32, T. 2 S., R. 2 E., 2 to 3 miles 
northeast of Springer, Carter County. 
Discussion.—This species is closest to Glyptorthis bellarugosa of any described 
in this paper. It differs, however, in the possession of a finer sculpture and more 
convex valves. 
GLYPTORTHIS RARA Cooper, new species 
Plate 44, B, figures 6-10 
Small, characterized by its great width and few strong imbrications. Orna- 
mentation consisting of 20 costae interrupted by 8 strong imbrications. Second- 
ary costae intercalated at about the middle. — 
