PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 489 
Same formation in Vermont: Just north of the neck of Providence Island, 
Plattsburg (15’) Quadrangle. 
St. Martin formation in Quebec: At Belanger, 2 miles south of Cap St. Mar- 
tin, Quebec. 
Discussion.—This species is characterized by some primitive characters such 
as the direct costae, a fairly strongly sulcate brachial valve, and wide hinge. 
These features give the shell a distinctly hebertelloid appearance, but the pedicle 
muscle scars are those of Mimelia. The species is closest to M. nuclea but dif- 
fers from that species in its more regular form, wider hinge, and more convex 
valves. 
MIMELLA WARDELLANA Cooper, new species 
Plate 90, D, figures 35-38 
Shell of about medium size for the genus, subrectangular in outline, wider than 
long. Sides fairly strongly rounded; anterior margin gently rounded to nearly 
straight ; anterior commissure broadly uniplicate. Multicostellate, costellae low, 
rounded, crowded, about 13 in 5 mm. at the front margin. 
Pedicle valve moderately convex in lateral profile with the most convex part 
in the posterior half, anterior half somewhat flattened. Anterior profile broadly 
and moderately convex. Umbonal region swollen; median region moderately 
convex ; anteromedian half depressed to form a shallow and wide sulcus. Flanks 
bounding sulcus gently swollen. Lateral and posterolateral slopes long and only 
moderately steep. Tongue broad and rounded. 
Brachial valve slightly deeper than the pedicle valve, fairly strongly convex 
in lateral profile and with the maximum convexity in the median region; anterior 
profile strongly convex with the maximum height of the arch in the median 
region and with long and steep slopes to the margins. Umbonal and median re- 
gions inflated ; anteromedian area forming a moderately broad but indistinct fold. 
Lateral descent from median region long and steep to the margins and postero- 
lateral extremities. 
Pedicle interior with muscle field subquadrate in outline, the diductor tracks 
narrow and nearly parallel, the adductor scars situated on a tonguelike elevation 
protruding slightly anterior to the front margin of the field. Brachial valve with 
deep notothyrial cavity, high cardinal process, and stout median ridge. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype (brachial valve)........ ? 14.9 20.9 13.5 6.7 
Paratype (pedicle valve 117055b).. 16.3 ? 20.9 15.0 ? 6.5 
Types.—Holotype: 117055a; figured paratype: 117055b; unfigured paratype: 
117055¢,d. 
Horizon and locality Wardell formation in Tennessee: In Raccoon Valley, 
$ mile northeast of Fleanor Mill, Powell Station (T.V.A. 137-SE) Quadrangle. 
Discussion.—This species is characterized by strongly convex valves and fine 
