PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 809 
Types.—Lectotype: 97544a ; paratypes: 97543a-c; figured hypotypes: 794194, 
d-g, 110985, 110993a-h, 111798a,b, 117549a, 117550b,d, 117551g,l,n,q, 124231a,b; 
measured hypotypes: 79419b, 117550c, 117552. 
Horizon and locality—Oranda formation in Virginia: North of the road 
0.6 mile northwest of Linville Station; just west of the junction of Virginia 
County Highways 617=910, and 777, on 777, 4 mile north of Green Mount 
Church, Broadway (15’) Quadrangle. Along the railroad 4 mile west of Stras- 
burg; on U. S. Highway 11, 2 miles southwest of Strasburg, Strasburg (15’) 
Quadrangle ; just east of Battlefield Crystal Caverns, 1 mile north of Strasburg ; 
Bowman Farm, 0.3 mile east of U. S. Highway 11, south edge of Woodstock, 
Edinburg (15’) Quadrangle; south side of U. S. Highway 33, 0.2 mile west 
of Harrisonburg city limits, Harrisonburg (15’) Quadrangle. 
Basal Martinsburg formation in Virginia: 0.6 mile northwest of Linville Sta- 
tion, Broadway (15’) Quadrangle. 
Martinsburg formation (part with Brongniartella=Salona) in Virginia: On 
Virginia County Highway 617=910, 0.15 mile north of Green Mount Church, 
Broadway (15’) Quadrangle. 
Oranda formation in Pennsylvania: 1 mile northwest of Guilford Springs, 
24 miles southwest of Chambersburg, Chambersburg (15’) Quadrangle; Carlisle, 
Carlisle (15’) Quadrangle; 1 mile south of St. Thomas, Mercersburg (15’) 
Quadrangle. 
Salona formation in Pennsylvania: On Fishing Creek at Salona, Lock Haven 
(15’) Quadrangle. 
Dark shale under Eureka quartzite in Nevada: In the north-facing nose of hill 
8167, and 4.2 miles north-northeast of Martin Ranch, Monitor Range; under 
2 knobs of Eureka quartzite, north side canyon, 3.1 miles N. 32° E. of Blair 
(Segura) Ranch, Antelope Mountains, Roberts Mountains (1°) Quadrangle. 
Discussion.—This species can generally be recognized by its large size, usually 
strongly convex pedicle valve, the beautiful ornamentation and the elaborate 
wrinkling of the posterior margins of both valves. As here described the species 
occurs in the Oranda and succeeding Salona formation, particularly near Green 
Mount Church north of Harrisonburg. 
Eoplectodonta alternata was originally inadequately described, the description 
consisting of two lines and the comparison being made to another species belong- 
ing to a different genus. The cotypes consist of four specimens, all of them poor. 
The best specimen, 97544a, is selected as lectotype. This specimen shows the 
ornamentation and the general form of the species, but no other details are 
preserved. 
This species is quite variable in profile and outline. Some of this variability has 
to do with age of the specimens and some of it with preservation. The younger 
specimens are flatter than the older ones and the beak is often visible when the 
shell is viewed from the full exterior. In the older adults the beak migrates an- 
teriorly as the shell grows, and the beak is obscured in the same view by the 
swollen umbonal region. The development of the fold on the pedicle valve is 
also a variable feature. In some specimens no distinct fold is visible, but in others 
