PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 979 
REUSCHELLA VESPERTINA Cooper, new species 
Plate 186, C, figures 11, 12; plate 260, B, figures 6-10 
Shell of medium size for the genus, wider than long, rectangular in outline; 
hinge slightly narrower than the midwidth; sides slightly oblique; anterolateral 
extremities narrowly rounded; anterior margin broadly rounded ; anterior com- 
missure strongly sulcate; costellae numbering Io to 12 in 5 mm. at the anterior 
margin of a large specimen. 
Pedicle valve gently concave in lateral profile, flat or gently concave in an- 
terior profile; umbo narrowly convex to carinate and extended anteriorly to the 
front margin as a strong, narrow fold. Flanks bounding fold flat to concave; 
sides deflected strongly in the direction of the pedicle valve. Interarea apsacline, 
moderately long. 
Brachial valve gently convex in lateral profile and broadly convex in anterior 
profile but with the sides steep. Umbo and medial region deeply sulcate, the 
sulcus extending to the anterior margin. Flanks bounding sulcus narrowly 
rounded, slopes of flanks steep; posterolateral extremities deflected toward the 
brachial valve. 
Interior unknown. 
Measurements in mm.—Holotype, length 21.2, length of brachial valve 21.7, 
midwidth 27.2, hinge width 27.0, thickness 6.4. 
Types.—Holotype: 124230a; figured paratypes: 123255b,c; 124230b; un- 
figured paratype: 123255a. 
Horizon and locality.—Upper part of the dark shale under the Eureka quart- 
zite in Nevada: Under two knobs of Eureka quartzite, north side of canyon, 
3.1 miles N. 32° E. of the Blair (Segura) Ranch, Antelope Mountains; on the 
north-facing nose of hill 8167, Martins Ridge, Monitor Range, Roberts Moun- 
tains (1°) Quadrangle. 
Discussion.—This species is characterized by the prominence of its fold and 
sulcus and the strongly deflected sides and posterolateral extremities. It differs 
from R. americana in not attaining the great size of that species, in having a 
broader fold and sulcus and more subdued costellae. This species is common 
in the upper part of the dark shales below the Eureka quartzite, but well- 
preserved specimens are rare. 
Family LINOPORELLIDAE Schuchert and Cooper, 1931 
Dalmanellacea having a cruralium in the brachial vave. 
LATICRURA Cooper, new genus 
(Latin latus, wide; crus, leg) 
Shells pionodemoid in outline and profile; with a long interarea, and open 
delthyrium. Anterior commissure sulcate. Surface multicostellate, with scat- 
tered, swollen, and hollow costellae as in Pionodema. Shell punctate. 
Inside the pedicle valve the dental plates are well developed, slender, receding. 
The anterior ends of the dental plates are continued along the floor of the valve 
