PELECYPODS 451 
with purplish rays arranged in various groupings; over all is a glossy 
epidermis. The hinge-teeth are very strong, and a prominent anterior 
lateral tooth on the left valve is noticeable. There is an external liga- 
ment; the pallial sinus is well marked, but not very deep. (Plate 
LXXXIII.) 
GENUS Chione 
There are three species on the west coast. This genus is 
very closely allied to Venus, and is considered by many to be 
only a subgenus of the latter. All three species are white, solid, 
heavy shells which exhibit the same scheme of sculpturing, 
namely, numerous longitudinal ribs crossed by larger and less 
frequent concentric ridges. 
C. simillima is shaped almost exactly like the east-coast Venus can- 
cellata, but its concentric ridges are very numerous and sharp. There is 
a strongly marked cordate lunule, and hardly any pallial sinus. Length 
one and a half to two inches. (Plate LXXXIIL.) 
C. succincta has fewer concentric ridges and has a large lunule. 
There are purple zones within and touching the heavy cardinal teeth. 
Length two and a half inches. (Plate LX XXIII.) 
C. fluctifraga has broad but flatter or well-rounded (not sharp) con- 
centric ridges, no lunule, a small ligament, a fairly deep pallial sinus, 
and a finely crenulated margin (within) all around the valves, except 
when interrupted by the hinge ligament. The shell is solid and shining, 
and marked by deep-purple zones within. Length one to two inches. 
Found in southern California. 
Genus Tapes 
This is a prominent genus of the Veneride. Its chief feature 
is the total want of lateral teeth. There are several large species 
in California. 
T. staminea, T. laciniata. These are the most noticeable species. 
The former is sold in the San Francisco markets as the “ hard-shell clam.” 
The shell of this species is from two to three inches in length and of 
somewhat less height, rounded, and heavy. The sculpturing consists of 
radiating ribs traversed by strongly marked growth-lines. The teeth 
are strong, and the pallial sinusis deep. 7. laciniata is much like the last, 
but its surface is reticulated by a crisscross design that is very striking. 
It also has a deep pallial sinus. These two species are of Southern range. 
They burrow in gravelly places, among stones, between tide-marks, and 
their presence may frequently be detected when walking along the beach 
at low tide by seeing a sudden jet of water ejected from a little hole in 
the mud or gravel. The aaa becoming alarmed at the approach of 
something, suddenly snaps shut its valves, and thus forces out some 
water through its siphons. The foot is very strong and often byssifer- 
ous in this genus. (Plate LX XXIII.) 
