PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 683 
R. 2 W., Grant County; quarry on Wisconsin Highway 81, 1 mile northwest of 
Ellenboro, Lancaster (30’) Quadrangle. 
PROTOZYGA PROFUNDA Cooper, new species 
Plate 143, A, figures 1-6 
Shell large for the genus, slightly wider than long, outline pentagonal. Strongly 
inequivalved ; posterolateral margins nearly straight, forming an angle of about 
110°; sides narrowly rounded and with the greatest thickness at about the 
middle ; anterior somewhat truncated ; anterior commissure strongly sulcate ; sur- 
face paucicostate, flanks with as many as 7 more or less distinct fine costae not 
reaching the beak; fold and sulcus finely but variably costate. 
Pedicle valve strongly convex in lateral profile, with the maximum curvature 
in the posteromedian part ; anterior profile with narrowly convex middle part and 
concave flanks; umbo narrowly swollen and continued anteriorly as a steep and 
narrow fold; sulcus in fold originating at about the middle, shallow and narrow. 
Flanks deeply concave but with flattened sides. 
Brachial valve moderately convex in lateral profile and with the maximum 
convexity at about the middle ; anterior profile broadly convex but with a median, 
deep sulcus; umbo sulcate, the sulcus continued anteriorly and forming a deep 
and narrow trench; tongue long and narrow; flanks bounding sulcus somewhat 
narrowly swollen and with steep lateral slopes. Interior as in the genus. 
Measurements in mm.—Holotype, length 5.8, width 6.6, thickness 4.0. 
Types.—Holotype: 117247a; unfigured paratype: 117247b. 
Horizon and locality—Trenton formation in Quebec: In a quarry near 
St. Francis de Salle, Montreal. 
Discussion—This species differs from all others here assigned to Protozyga 
by the great depth of its sulcus and the nearly complete costation of the flanks. 
PROTOZYGA ROTUNDA Cooper, new species 
Plate 140, B, figures 10-16; plate 140, H, figures 48-52; plate 140,I, figures 53-58 
Shell small, nearly circular in outline, strongly biconvex, beak approximately 
a right angle or slightly obtuse, sides strongly rounded, anterior margin pro- 
truding slightly, rounded. Surface smooth or with I or 2 short, obscure costae 
on the margins of the flanks near the fold or sulcus. 
Pedicle valve generally deeper than the brachial valve, strongly convex and 
with the greatest convexity at about the middle; beak strongly incurved and in 
old specimens closely pressed down on the umbo of the brachial valve; umbonal 
region gently convex in profile, narrowly convex in anterior view ; fold originat- 
ing on the umbo, not strongly elevated and extending to the anterior margin. 
Sulcus shallow ; appearing in the fold a short distance posterior to the anterior 
margin; flanks gently convex or nearly flat in profile and with steep slopes to 
the margin. Beak ridges short, not prominent. 
Brachial valve moderately to strongly convex depending on age, the older 
shells more rotund and deeper; anterior profile moderately convex. Umbonal 
