378 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
but in the later stages of growth the centrally situated teeth are 
obliterated by encroachment of the hgament. Interior unknown, but 
interior of margins appear to be smooth. 
Dimensions.—Length, 62 mm.; latitude, 62 mm.; diameter of single 
valve, 23 mm. | 
Notes——This magnificent species is apparently one of the largest 
of the west coast forms, equaling in size but not in convexity the Cre- 
taceous Glycymeris veatchii Gabb and its Eocene variety G. veatchii 
major Stanton. It also lacks the prominent groove which sepa- 
rates the dorsal posterior angle from the rest of the shell in the earlier 
forms. It is distinguishable from Glycymeris gabbi Dall from Coos 
Bay, Oregon, the next largest Miocene species, by its unsymmetrical 
outline, its much greater size, relatively greater convexity, closer set 
ribs, and peculiar wavy incremental sculpture. The species is be- 
lieved to be characteristic of the Vaqueros formation (lower Miocene). 
Named in honor of Dr. John Casper Branner, professor of geology, 
Leland Stanford Junior University. 
Type.—Letft valve, Cat. No. 165455, U.S.N.M. (Locality No. 12.) 
Horizon.—V aqueros formation, lower Miocene. 
Localities—Santa Cruz quadrangle, San Mateo County, locality 
No. 12, Mindego Creek, 1 mile above its confluence with Alpine Creek. 
(R. Arnold, H. Holly, lL. C. Mills.) 
Genus CARDIUM (Linnzeus) Lamarek. 
Subgenus TRACHYCARDIUM Morch. 
CARDIUM (TRACHYCARDIUM) VAQUEROSENSIS, new species. 
Plate XXXIV, fig. 3. 
Description.—Shell attaiing a length of over 100 mm., nearly as 
high as long, subcircular in outline, very convex, quite thick; umbo 
prominent, protruding above hinge-line, subcentral, turned shghtly 
toward anterior extremity; anterior extremity regularly rounded, 
posterior one somewhat flattened, forming two faint angles, the lower 
one of which is connected with the umbo by quite a pronounced angle 
in the surface of the shell, upper angle about two-fifths length of shell 
from the umbo. Sculpture consists of about 34 tall, squarish ribs 
separated by deep channeled interspaces about equal in width to the 
ribs; the ribs become less and less conspicuous toward the ends of the 
shell; incremental sculpture well developed, and making a convex 
bow upward toward the umbo on top of each rib. Hinge and interior 
probably similar to (. quadrigenarium. 
Dimensions.—Length, 65 mm.; altitude, 60 mm.; diameter of single 
valve, 29 mm. 
_ Notes.—This species is doubtless the precursor of C. quadrigen- 
arium Conrad, from the Pleistocene and Recent fauna, but differs 
