no, 1617.. NEW CRETACEOUS AND TERTIARY FOSSILS—ARNOLD BHC 
much longer, but narrower posteriorly, than 2’. coopera Gabb fron 
the Pliocene to Recent fauna; and is much larger, broader and more 
closely sculptured than Y. impressa Conrad from the Oligocene and 
Miocene. Distinguished from Y. supramontereyensis, new species, 
which occurs in ‘The Miocene above the Monterey, by its shorter and 
broader posterior end. 
Name derived from its stratigraphic position in the lower Miocene 
below the Monterey (middle Miocene) formation. 
Type.—Cat. No. 165459, U.S.N.M. (Locality 35.) 
Horizon.—Vaqueros formation, lower Miocene. 
Localities —Santa Cruz quadrangle; San Mateo County, localities 
Nos. 1 and 2, on hill and beside road, respectively, three-fourths 
mile northeast of north end of Searsville Lake (R. Arnold) ; locality 
No. 35, on San Francisquito Creek, just below dam, 14 miles south- 
west of Stanford University (R. Arnold; Fay). 
Genus GLYCYMERIS Da Costa. 
GLYCYMERIS BRANNERI, new species. 
Plate XXXIV, fig. 1. 
Description.—Shell averaging nearly 70 mm. in length, about as 
wide as long, suborbicular, equivalve, bilaterally unsymmetrical, con- 
siderably convex for one of this genus, thick and heavy; umbo some- 
what anterior to center, protruding beyond hinge line and turned 
shehtly toward the front; anterior dorsal margin straight, sloping 
steeply from umbo; anterior extremity quite sharply rounded, and 
located above center line of shell; posterior dorsal margin straight, 
sloping less steeply than anterior; posterior extremity protruding 
obliquely downward and backward, regularly rounded, located below 
center line of shell; posterior dorsal and ventral margins join in a 
faintly defined angle considerably above and in front of the extreme 
end of the shell. Surface sculptured by numerous flat to concave- 
topped, close-set, radiating ribs (about 55 discernible in the type). 
relatively much broader toward the middle of the shell and becoming 
narrower and less well defined toward either end; in the later stages 
of growth a raised beaded intercalary line occupies the interspace 
and (in the type) rises above the level of the ribs; prominent incre- 
mental lamellz cross the ribs, bowing convexly upward toward the 
-umbo; they are straight 6n the sides and across the top of the ribs, 
_ and become less prominent and more closely set toward the periphery 
in the adult shell. Hinge with 5 or 6 boomerang-shaped teeth, with 
angle toward the umbo, on either side of a centrally divaricately 
striated broad ligamental area; the teeth in the young form a semi- 
circle below and extending on either side beyond the ligamental area. 
