PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 647 
or 4 costae, the fold having 4 or 5 costae, and the flanks marked by as many as 
10 costae. 
Pedicle valve gently convex in lateral profile with the maximum curvature be- 
tween the umbo and the middle; anterior profile flattened or concave medially 
and with steep lateral slopes. Sulcus originating 5 or 6 mm. anterior to the beak. 
Sulcus deepening anteriorly from the middle of the valve, never very deep even 
at the anterior end. Tongue moderately long. Flanks flattened and with moder- 
ately steep slopes. 
Brachial valve of about equal depth to that of the pedicle valve; lateral pro- 
file gently convex; anterior profile broadly convex and with precipitous sides. 
Umbo gently swollen, narrowly sulcate. Fold originating near the middle of the 
valve, not strongly elevated even at the front. Flanks swollen and only slightly 
depressed below the fold; lateral slopes steep. 
Measurements in mm.— 
Brachial 
Length length Thickness Width 
LOA ee ne 12.0 II.I ite Hy, 8.7 
Paratype Wrasse. Meee ert eke 10.8 10.0 11.8 7.6 
Types.—Holotype: 117224b; unfigured paratype: 1172244. 
Horizon and locality—Decorah formation (Guttenburg member-Rhimidictya 
bed) in Minnesota: In the Mississippi River bluffs at St. Paul. 
Discussion.—This species has a broad, low fold and sulcus, broad outline with 
the midwidth forming the widest part, and a fairly large apical angle. The species 
is somewhat intermediate between R. minnesotensis and R. colei. From the 
former it differs in having a much less rotund profile and smaller and more 
numerous costae; it differs from the latter in being much smaller and having a 
wider fold. It appears to be a more robust shell than R. missouriensis and differs 
from R. decorahensis in being wider and more numerously costate. 
ROSTRICELLULA RAYMONDI Cooper, new species 
Plate 130, E, figures 25-34; plate 130, F, figure 35; plate 132, C, figures 11-18 
Camarotoechia orientalis RAyMoND (part), Ann. Carnegie Mus., vol. 7, No. 2, p. 223, pl. 35, 
figs. 19-22, 24-31 (not 32 and 33), IgII. 
Shell of about medium size for the genus, subelliptical to subtriangular in out- 
line; beak ranging from a right angle to obtuse; sides narrowly rounded; front 
margin subnasute; surface costate, generally 3 costae marking the sulcus (occa- 
sionally 4) and 4 the fold (occasionally 5), with the flanks occupied by 6 or 7 
costae, the last 3 or 4 obscure. 
Pedicle valve gently convex in lateral profile with the most convex part lo- 
cated in the posterior half; umbonal region narrowly convex; sulcus originating 
about 5 mm. anterior to the beak, deep and occupying more than half the width 
at the front; tongue moderately long; flanks flat in profile and with moderate 
slopes to the margins. Costae forming margin of sulcus elevated strongly an- 
teriorly above the sulcus to form pointed extremities. 
Brachial valve about equal to the pedicle valve in depth, gently convex in 
