PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 609 
Genus PORAMBONITES Pander, 1830 
Porambonites PANvER, Geogn. Russ. Reiches, p. 95, 1830.—TrEIcHERT, Neues Jahrb. Mineral., 
Geol. and Paleont., Beil., Bd. 63, Abt. B, p. 177-246, 1930—ScHUCHERT and Cooper, 
Mem. Peabody Mus. Nat. Hist., vol. 4, pt. 1, p. 102, 1932. 
PORAMBONITES ? UMBONATUS Cooper, new species 
Plate 107, B, figures 4-11 
Porambonites ? sp. Utricu and Cooper, Geol. Soc. Amer. Special Pap. 13, p. 242, pl. 53C, 
fig. 21 (not 27), 1938. 
Shell large, wider than long, broadly elliptical in outline; valves subequally 
convex. Lateral margins broadly rounded ; anterior margin subnasute; anterior 
commissure uniplicate. Surface marked by rows of small pits separated by fine 
costellae, about 3 of the latter in 1 mm. near the anterior margin of the brachial 
valve. 
Pedicle valve moderately convex in lateral profile with the maximum convexity 
slightly posterior to the middle; anterior profile broadly convex; umbonal and 
median regions swollen ; sulcus originating at the middle, shallow, wide, not in- 
creasing greatly in depth anteriorly. Tongue long, wide, and narrowly rounded. 
Flanks moderately swollen and with moderately steep slopes. 
Brachial valve gently convex in lateral profile, with the umbonal region 
rounded but the anterior two-thirds flattened. Fold low, somewhat narrowly 
rounded, originating at the middle. Umbo and median region inflated; flanks 
moderately inflated and with moderately steep slopes. Interior with 2 widely 
divergent brachiophore supporting plates. 
Measurements in mm.—Holotype, length 23.2, brachial length 22.8, width 
27.3, hinge width 12.9, thickness 14.2. 
Types.—Holotype: 111373a; figured specimen: 102310. 
Horizon and locality—Pogonip group (lower part Rhysostrophia zone) in 
Nevada: About 1 mile above the mouth of Ikes Canyon, south side of canyon, 
Toquima Range, Roberts Mountains (1°) Quadrangle. 
Same formation in California: In Nopah Range, Inyo County. 
Discussion.—This species proved to be very rare in the Ikes Canyon locality. 
It is characterized by its low fold and shallow sulcus and the fine ornamentation. 
If differs from P. reticulatus Pander in the first two of the above characters. It 
also differs in having widely divergent brachial plates rather than nearly parallel 
ones. 
PORAMBONITES ? sp. 1 
Plate 108, H, figures 40-42 
Represented by one complete but crushed pedicle valve and another frag- 
mentary pedicle valve showing sessile spondylium. Syntrophoid in habit, wider 
than long, with narrowly rounded sides. Lateral profile moderately convex ; an- 
terior profile broadly convex; tongue short, narrowly rounded. Flanks gently 
inflated and with moderate slopes. Teeth long, sharp, dental plates strong, an- 
terior of sessile spondylium thickened, tapered, and elevated; median ridge not 
