PART I CHAZYAN AND RELATED BRACHIOPODS—-COOPER 323 
Discussion—This species is difficult to separate from C. Della (Schuchert 
and Cooper) because the details of the ornamentation are very close. Neverthe- 
less, C. magna has somewhat stronger and more closely crowded costellae. Fur- 
thermore, the brachial valve is generally more concave than that of C. bella. In 
C. magna the brachial valve is fairly strongly concave in young individuals, but 
the concavity becomes less anteriorly as the shell grows. C. bella on the other 
hand is nearly planoconvex in the young and stays that way throughout life. 
CYRTONOTELLA MINOR Cooper, new species 
Plate 41, B, figures 4-7 
Small for the genus, wider than long, nearly planoconvex ; surface costellate ; 
costellae narrowly rounded, elevated with striae slightly wider than the costellae ; 
11 costellae in 5 mm. at the front margin. 
Pedicle valve strongly convex in lateral profile; greatest convexity at about 
the middle; anterior profile narrowly convex in the median region with long and 
moderately steep slopes to the lateral margins ; umbo narrowly swollen, the swell- 
ing continued into the midregion and indistinctly to the anterior margin. Lateral 
and umbonal slopes moderately steep. Umbo protruding posterior to the pos- 
terior margin; beak incurved ; interarea short, orthocline. 
Brachial valve with sulcate umbo ; sulcus narrow, deepening toward the middle 
but becoming shallow and nearly obsolete at the front margin; flanks bounding 
sulcus nearly flat. 
Measurements in mm.—Holotype, length 11.9, brachial length 11.3, width 
15.1 ?, thickness 4.0. 
Types.—Holotype: 116900a ; unfigured paratype: 116900b. 
Horizon and locality Lincolnshire formation in Tennessee: On the east side 
of the road 4 mile north of Eidson, Kyles Ford (T.V.A. 170-SE) Quadrangle ; 
on the strike of the same bed as above, 4 mile northwest of Eidson, Kyles Ford 
(T.V.A. 170-SE) Quadrangle. 
Discussion.—This species is represented by three poor specimens only. It is 
finely costellate and more so than any of the other species herein described. It is 
evidently a rare species in the Lincolnshire and was found only in the shaly beds 
at Eidson. 
CYRTONOTELLA SUBPLANA Cooper, new species 
Plate 39, C, figures 12-15 
Shell large, wider than long, with the hinge about equal to the width at the 
middle. Cardinal extremities a right angle. Lateral margins nearly straight ; 
anterior margin fairly strongly rounded. Anterior commissure not folded. Sur- 
face multicostellate, costellae low and subangular and separated by interspaces 
wider than the width of the costellae. About 6 or 7 costellae occupying 5 mm. 
at the median front margin; about 90 costellae occur on the valve. Costellae 
crowded on the cardinal extremities. Fine ornament consisting of strong con- 
centric fila. 
Pedicle valve moderately convex in lateral profile; anterior profile with great- 
