PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 597 
common with camerelloid shells. The median septum is best defined at the front 
of the spondylium but is not extended for a great distance anterior to the 
anterior end of that structure. 
The most important features are in the interior of the brachial valve. The 
brachiophores and their supports are like those of Camereila, but instead of meet- 
ing the median septum in the direction of the brachial valve they are attached 
to the floor to form a narrow notothyrial cavity rather than a short cruralium as 
in Camerella. In Plectocamara the median septum is reduced to a mere ridge 
extending anteriorly of the notothyrial cavity for a short distance and dividing 
the small adductor impressions. 
PLECTOCAMARA ASEPTATA Cooper, new species 
Plate 122, C, figures 22-26; plate 122, D, figures 27-29; plate 123, B, figures 7-11; plate 123, C, 
figures 12-16; plate 123, G, figures 32-54; plate 126, E, figures 25-29 
Small subtriangular to subelliptical in outline, wider than long, widest slightly 
anterior to the middle. Beak obtuse, sides straight ; anterolateral extremities nar- 
rowly rounded. Anterior margin straight. Surface costate, costae subangular, 
with the flanks marked by 7 or 8 and the fold by 3 or 4, with 2 or 3 costae in the 
sulcus. 
Pedicle valve gently convex in lateral profile and broadly convex in anterior 
profile. Beak short, suberect. Umbo gently convex. Sulcus originating 14 to 2 
mm. anterior to the beak, strongly depressed anteriorly to form a fairly sharply 
geniculated tongue. Flanks bounding sulcus flattened to slightly convex and with 
gentle slopes to the margin in the anterior region and steepening posteriorly. 
Brachial valve moderately convex in lateral and anterior profiles ; fold originat- 
ing about I mm. anterior to the beak, moderately strongly elevated anteriorly. 
Flanks depressed below fold, gently rounded and with gentle slopes to the 
margins. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
GIP Vee cos aves 1S cot chick tees = 6.1 5.4 7.2 4.1 
Pasatype.(z1rg6rb)i. 0. 2.0... e208 5.6 5.2 6.5 3.4 
. CF EPIHIC).  sasdees 1. oe 5.2 4.8 6.1 3.9 
Types—Holotype: 111361a; figured paratypes: 111361b,c, 117180b, 117181, 
117182a-d ; unfigured paratypes: 111370a, 117182e; figured specimen: 117180a. 
Horizon and locality—Lower Benbolt formation in Virginia: 14 miles west 
of Rye Cove at the Brick Church, Clinchport (T.V.A. 188-NW) Quadrangle ; 
0.2 mile south of the middle fork of Moccasin Creek, 15 miles south of Hanson- 
ville, Hansonville (T.V.A. 205-SW) Quadrangle; south side of Mount Hagan 
Church, Hilton (T.V.A. 197-NW) Quadrangle. 
Benbolt formation in Tennessee: At Evans Ferry, U. S. Highway 25E, north 
of Indian Creek, Howard Quarter (T.V.A. 162-NW) Quadrangle. 
From limestone with Oligorhynchia in Virginia: 4 mile southeast of Richpatch, 
Eagle Rock (15’) Quadrangle. 
