PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 365 
GLYPTORTHIS CONCINNULA Cooper, new species 
Plate 43, F, figures 22-43 
Small to medium-sized for the genus, wider than long, with the hinge form- 
ing the greatest shell width or so narrowed as to be less than the width near 
the middle. Lateral margins ranging from straight and sloping medianly to 
gently convex; anterior margin straight or slightly curved. Surface multicostel- 
late, the costellae elevated and subangular and separated by spaces as wide or 
wider than the costellae. Three generations of costellae may be counted: a set 
originating at the beaks, a secondary set, few in number, intercalated near the 
middle and a ternary set appearing a short distance posterior to the margin. 
From 6 to 9 costellae appear in 5 mm. at the front margin depending on the 
amount of anterior intercalation. From 20 to 36 costellae may be counted on a 
valve. About 3 imbricating lamellae in the space of 1 mm. near the middle. 
Pedicle valve in lateral profile with maximum convexity in the posterior half; 
in anterior profile broadly convex with moderately sloping sides. Umbo full, this 
fullness extended for the median length as an indistinct fold. Lateral slopes long 
but only moderately steep as most of the fullness is concentrated in the median 
area. Beak slightly incurved ; interarea nearly flat, short. Delthyrium narrow. 
Interior with short, thick dental plates ; moderately deep delthyrial cavity ; muscle 
field heart-shaped with adductor field slightly elevated, large diductor impres- 
sions but small adjustor scars. 
Brachial valve most convex in the posterior half in lateral profile but broadly 
and gently convex and with the median part sulcate in anterior profile. Sulcus 
originating at the umbo, prominent, widening and deepening anteriorly, variable 
in depth and width. Sulcus with 2 costellae on the umbo, bifurcating in a short 
distance to produce 4, and this number augmented by intercalations of the ternary 
set near the front margin. Flanks moderately convex with short but fairly steep 
umbonal slopes and with lateral slopes becoming less steep anteriorly. Interarea 
short. Interior of brachial valve with short, stout brachiophores, prominent 
median ridge and large adductor field. The anterior adductor scars are each 
divisible into 2 impressions; the posterior scars small. Pallial marks not well 
preserved in either valve. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
PAGIAV PE le cics Gas tye ess 7.5 6.2 8.4 yi 4.8 
Paratype (110025a)..... 8.3 7.6 10.1 9.5 5.4 
o (10026) eine eae WE 6.9 8.7 IP 4.6 
A (T1603ED) sur a. 6.2 5.5 7.4 6.1 By 
he (7100358). °.\.: 8.3 7.8 10.4 9.6 4.4 
i (m100274)) Fa0. 7.60 6.8 8.0 72 5.2 
Types.—Holotype: 116931a; figured paratypes: 110025a, 110027a,b, 
110028a,b, 110034a,b,e,g, 110035a; unfigured paratypes: 110026, 110028c-e, 
110034c,d,f; 116931b. 
Horizon and locality—Little Oak formation in Alabama: 4 mile northeast of 
