B82 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
UPPER MIOCENE SPECIES. 
ILO YIP OID A. 
Genus YOLDIA, Moller. 
YOLDIA SUPRAMONTEREYENSIS, new species. 
Plate XXXV, fig. 9. 
Description.—Shell attaining a length of 32 mm., width about two- 
thirds length, oblong, rounded in front, somewhat attenuated, angular 
and slightly gaping behind, eompressed; margin smooth; umbo not 
prominent, curving backward, anterior, being about 48 per cent of 
the length of the shell from the exterior extremity; anterior dorsal 
_ margin slightly convex, anterior extremity quite evenly rounded; 
posterior dorsal margin slightly concave and turned up at the extrem- 
ity, meeting the ventral margin in a right angle slightly above and 
anterior to the curved extremity; a very faint carima, separated from 
the dorsal margin by a faint groove, extends from the umbo to the 
posterior extremity. Surface sculptured by numerous, regular, nar- 
row, incremental lamelle, as in VY. submontereyensis, new species. 
Hinge and teeth similar in a general way to ’. coopert. (See note 
following description of ¥’. swhmontereyensis, p. 316.) 
Dimensions.—Leneth, 37 mm.; latitude, 20.2 mm.; umbo to ante- 
rior extremity, 18 mm. (48 per cent of length). 
Notes.—This species is characterized by its long posterior extremity, 
which has a relatively greater length than that of any of the other 
west coast species. 1. swpramontereyensis is closely allied to Y. 
submontereyensis, new species from the lower Miocene, but is easily 
distinguishable by its long posterior extremity. 
Name derived from its stratigraphic position in the upper Miocene 
above the Monterey (middle Miocene) formation. This species oc- 
curs in the bed overlying the basalt flow near Stanford University. 
Type.—.s8.J.U., No. 1067. (Locality No. 4.) 
[orizon.—Upper Miocene. 
Localities—Santa Cruz quadrangle, Santa Clara County, locality 
No. 4, in * Tusk Gully ” near road, 24 miles south of Mayfield; local- 
ity No. 42, on west face of hill facing road, one-half mile west of 
locality No. 4. (R. Arnold.) 
Genus PERIPLOMA Schumaeher. 
PERIPLOMA SANCTACRUCIS, new species. 
Plate XXX/YV, fig. 8. 
Description.Shell attaining a length of 40 mm., width nearly 
five-eighths of length, oblong, inequivalve, inequilateral, anterior end 
rounded, posterior shorter and more contracted; right valve gibbous, 
