632 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
ROSTRICELLULA ? ANGULATA Cooper, new species 
Plate 134, D, figures 33-46 
Slightly wider than long, triangular in outline, apical angle slightly less than 
go°. Posterolateral margins straight ; anterolateral extremities narrowly rounded ; 
anterior margin broadly rounded. Costate, 3 costae on the fold, 2 in the sulcus, 
and 6 to 8 on the flanks. 
Pedicle valve gently convex in lateral profile, broadly and gently concave in 
anterior profile; sulcus originating at about the middle, deepening rapidly. 
Tongue moderately long. Anterolateral extremities prominently elevated above 
the sulcus. Flanks flattened but with steep slopes. 
Brachial valve deeper than the pedicle valve and with low convexity in lateral 
view, most convex in the umbonal region but flattened anteriorly. Anterior pro- 
file broadly and gently convex. Umbo sulcate; fold originating about 4 mm. an- 
terior to the beak; fold flattened in both profiles, elevated strongly only at the 
anterior end. Flanks gently rounded and with moderate slopes. 
Measurements in mm.— 
Brachial 
Length length Width Thickness 
PLGIGEWDE secre ote ce pee 12.7 12.0 14.5 7.1 
Paratype ©. GCIA72EAD) i. eves mee e's 14.0 13.0 14.2 8.6 
* (TIZSTAC) . ese cass oh 12.5 11.2 12.4 8.0 
Types.—Holotype: 117214a; figured paratype: 117214b; unfigured paratype: 
I17214c. 
Horizon and locality—Lower part of dark gray shale in Eureka group, in 
Nevada: On the north-facing nose of hill 8167 on Martins Ridge, Monitor 
Range, Roberts Mountains (1°) Quadrangle. 
Discussion.—This species is characterized by distant, strong, angular costae 
and by the presence of only 2 costae in the sulcus. This species differs from 
R. truncata, the only other one like it, in having only 2 costae in the sulcus, in 
having 5 or 6 costae on the flanks rather than 4, and in having a narrower apical 
angle and a narrower fold. 
ROSTRICELLULA BASALARIS Cooper, new species 
Plate 132, E, figures 21-29; plate 132, F, figures 30-37; plate 137,C, figures 20-26; 
plate 137, D, figures 27-33; plate 137, F, figures 37-46 
Rostricellula pristina Cooper and Coorer (not Raymond), Bull. Geol. Soc. Amer., vol. 57, 
p. 112, pl. 2, figs. 16, 17, 1946. 
Shell of about medium size, triangular in outline, length and width about equal ; 
apical angle slightly less than 90°. Fold marked by 3 or 4 costae, the sulcus by 
2 or 3, and the flanks by 5 or 6. 
Pedicle valve slightly less deep than the brachial valve, gently convex in lateral 
and anterior profiles ; sulcus originating 2 to 3 mm. anterior to the beak, deepen- 
ing anteriorly and occupying about half the width at the front, tongue moder- 
ately long. Costae bounding sulcus strongly elevated at anterior end; flanks 
flattened and moderately steep. 
