PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER g2I 
Types—Holotype: 117840a ; figured paratype: 117840b; unfigured paratype: 
117840. 
Horizon and locality Wardell formation in Tennessee: On the north side 
of the road 1.1 miles northeast of Lee Valley, Lee Valley (T.V.A. 171-NW) 
Quadrangle; 2 miles northeast of Thorn Hill, Avondale (T.V.A. 162-SW) 
Quadrangle. 
Davis’ store, 5 miles west of Eidson, Hawkins County; military coordinates 
719410N, 2746920F, hill west of west fork of center branch of Notchy Creek, 
Avondale (T.V.A. 162-SW) Quadrangle. 
Same formation in Virginia: 4 mile west of the Danlboone Siding on U. S. 
Highway 58, Gate City (T.V.A. 188-NE) Quadrangle. 
Discussion.—This species is similar to O. speciosa and to O. inquassa but 
differs from both of them in having the brachial valve gently concave. 
OPIKINA TRANSITIONALIS (Okulitch) 
Rafinesquina transitionalis OkutitcH, Canadian Field-Nat., vol. 49, No. 6, p. 97, pl. 1, 
figs. 3, 4, 1935. 
Opikina transitionalis (Okulitch) SAtmon, Journ. Paleont., vol. 16, No. 5, p. 505, pl. 87, 
figs. 15-18, 1942-—Witson, Geol. Surv. Canada, Bull. 8, p. 93, 1946 (specimen figured 
rejected by Salmon and placed in O. wagneri (Okulitch) ). 
Types.—Holotype: Peter Redpath Mus., McGill Univ., Montreal. 
Horizon and locahity.—Lowville and Leray formations in Quebec: At Pointe 
Claire. “One of the most common species of Opikina in North America” accord- 
ing to Salmon (1942, p. 590). 
Discussion.—This species has been widely identified by Salmon and others 
from Middle Ordovician rocks, but the species could not be identified in any of 
the collections herein described. It is suggested that its affinities are with the 
more northern areas of outcrop of Black River-Early Trenton strata. 
OPIKINA TRANSVERSA Cooper, new species 
Plate 244, C, figures 17-32 
Shell small for the genus, wider than long and with the hinge usually form- 
ing the widest part ; cardinal extremities subauriculate ; sides gently rounded and 
oblique ; anterior margin broadly rounded; finely costellate, 2 or 3 of the larger 
costellae occupying I mm. at the front margin. Posterior margin with oblique 
wrinkles. 
Pedicle valve strongly but unevenly convex in lateral profile, the maximum 
convexity located at or just anterior to the middle; anterior broadly and usually 
strongly domed; visceral region gently to moderately convex; geniculated por- 
tion somewhat narrowly rounded about half the surface length of the pedicle 
valve to the beak. Anterior slope gently convex, steep and longer than the lat- 
eral slopes which are also steep. Interarea short. 
Brachial valve with visceral region gently concave and surrounded by the 
strongly curved lateral and anterior margins. Brachial valve deepest just anterior 
to the middle. 
