PART? T CHAZYAN AND RELATED BRACHIOPODS—COOPER 369 
Pedicle interior with short, receding dental plates ; deep delthyrial cavity with 
well-impressed muscle area somewhat elevated at its anterior end; vascula media 
slightly divergent, short ; reniform ovarian markings moderately impressed. 
Brachial interior with deep notothyrial chamber, strongly elevated notothyrial 
platform ; thin cardinal process and stout divergent brachiophores. Median ridge 
low, extending to the middle. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
FLOLOLY pe: GrNe suceve: es « 14.6 127, 17.3 16.0 10.3 
Paratype (116934a). 14.3 14.1 16.9 ? 15.2 11.0 
Types.—Holotype: 116934b; figured paratypes: 116934a,c, 116933a,b; un- 
figured paratype: 116934d. 
Horizon and locality—Shippensburg formation (Pinesburg member-Echino- 
sphaerites zone) in Maryland: In a cut on U. S. Highway 40, just west of 
Conococheague Creek at Wilson, 7 miles west of Hagerstown, Williamsport 
(15’) Quadrangle. 
Botetourt formation in Virginia: On the south side of the road 0.2 mile east 
of Strasburg, Strasburg (15’) Quadrangle. 
Discussion.—This species is characterized by the obese valves and their nearly 
equal depth. The species is somewhat suggestive of large individuals of G. wir- 
ginica, but that is a wider form having a sulcate pedicle valve and a low fold on 
the brachial valve. Glyptorthis equiconvexa has a subquadrate outline and thus 
is quite unlike G. subcircularis which has strongly convex valves and a robust 
form. 
GLYPTORTHIS GLYPTA Cooper, new species 
Plate 48, B, figures 7-11; plate 108, A, figures 1-5 
Shell small for the genus, wider than long, with the hinge equal to, or slightly 
less than the greatest shell width, or forming the widest part. Cardinal extremi- 
ties varying from slightly acute to slightly obtuse. Lateral margins slightly con- 
vex; anterior margin broadly rounded. Anterior commissure slightly sulcate. 
Surface costate, costae narrowly rounded, interspaces broad; costae numbering 
about 15, some costae fasciculate in front by intercalation of a generation on one 
or each side of the primary costa. Lamellae distant on body of shell, crowded 
anteriorly in old specimens. 
Pedicle valve moderately convex in lateral profile; broadly convex in anterior 
profile. Fold generally low, not clearly perceptible in the young, most clearly 
defined by the strong elevation of the median costa in the posterior half; flanks 
descending gently to the lateral margins. Beak extending slightly posterior to 
the posterior margin. Interarea long, strongly apsacline. Interior with elongate, 
narrow diductor impressions and strongly elevated adductor track. Pallial 
sinuses not well defined. 
Brachial valve moderately convex in lateral profile with the most strongly 
arched part in the posterior third; anterior profile very broadly and gently con- 
