610 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
protruding anterior to spondylium. Exterior marked with strong rows of pits 
separated by narrow costellae. 
Measurements in mm.—117177, length 14.0, width 19.1. 
Figured specimen.—117177. 
Horizon and locality—Pogonip group in California: In the hills on the west 
side of Racetrack Valley opposite Quartz Spring, Uhebe Peak (15’) Quadrangle. 
Discussion.—This species, of which only a single good pedicle valve is known, 
is smaller, more transverse, and more coarsely ornamented than P. ? umbonata. 
It is probably from a lower horizon although its precise position is not known. 
PORAMBONITES ? sp. 2 
Plate 107, A, figures 1-3 
Length and width about equal, subhexagonal in outline; sides narrowly 
rounded ; posterolateral margins straight, forming an angle of about 120° ; antero- 
lateral margins nearly straight and continuous with the sharply pointed tongue. 
Umbonal region swollen; sulcus originating on the umbo, shallow, narrow, but 
widening and deepening anteriorly but not attaining more than a third the width. 
Flanks moderately convex with steep posterolateral slopes. Surface finely costel- 
late and pitted but details indistinct in this specimen. Interior with stout dental 
plates ; sessile spondylium thickened anteriorly but only slightly elevated at the 
front ; median ridge short and thick. Adductor field an oval scar at the anterior 
end of the sessile spondylium. 
Measurements in mm.—117179, length 19.1, width 20.8. 
Figured specimen.—117179. 
Horizon and locality—Lower Table Head series in Newfoundland: At Table 
Point. 
Discussion.—This species has a syntrophoid appearance like that of the pre- 
ceding specimen, but the ornamentation seems to be finer and the sulcus is longer 
and narrower. 
PORAMBONITES ? sp. 3 
Plate 106, D, figures 17-24 
Three specimens of a third species referrable to Porambonites? were taken 
from the Orthidiella zone in Nevada. The fine ornamentation and small pits 
suggest that all the specimens are immature. The largest is 8 mm. wide by 6 mm. 
long, but the margins are crushed. At its front margin this specimen has 4 or 5 
costellae in I mm. 
The other two specimens come from the siliceous residues produced by diges- 
tion of limestone from the Orthidiella zone east of Frenchman Flat. The largest 
specimen is probably a pedicle valve and is 4 mm. wide by 33 mm. long. Inside 
it has two somewhat divergent dental lamellae bounding a fairly wide and deep 
delthyrial cavity. The floor of the cavity between the plates is slightly thickened. 
The third specimen is a fragmentary one and is interpreted as the posterior part 
of the brachial valve. In this one the plates are shorter and are inclined toward 
each other slightly. The thickening between them is greater than that of the 
