download pdf

438 Avierican Seashells
smooth, even at the blunt, posterior end. Only 2 color phases: yellowish
white or with weak purplish rays. Subsequent biological studies may show
that this common beach species is a subspecies or cold-water form of varia-
bilis. Young specimens of variabilis from several southern states look suspi-
ciously like this so-called species.
Donax tu7indus Philippi Fat Gulf Donax
Northern shores of the Gulf of Mexico.
% to /4 inch in length, very obese, somewhat trigonal in shape, with its
beaks swollen and posterior end strongly truncate. Threads on the blunt
posterior end are heavily beaded, sometimes giving a cancellate appearance.
Narrow anterior end commonly with distinct, microscopic, distantly spaced,
incised, concentric lines. Color whitish with bluish, yellowish or pinkish
undertones. Rarely, if ever, rayed. Uncommon. Found in 2 to 3 feet of
water.
Donax denticulatus Linne (pi. 3 op) from the southwest Caribbean has
been erroneously recorded from our shores. It is i inch in length and char-
acterized by 2 curved, low ridges on the posterior slope of each valve and
by microscopic pin-points on the sides of the valves,
Donax striates Linne also a lower West Indian species is as large, but
characterized by a flat to slightly concave posterior slope which bears numer-
ous fine radial threads.
Donax gouldi Dall Gould's Donax
San Luis Obispo, California, to Mexico.
Plate 3iq
Common jorm: % inch in length, fairly obese, truncate at the posterior
end where the beaks are located. Shell glossy, smooth, except for numerous,
microscopic, axial threads at the anterior end. Exterior cream to white with
variable color rays of light-tan. Margins of valves commonly flushed with
purple. Interior stained with purple or bluish brown. Common on beaches,
especially in the north. Kno\\^n locally as the Bean Clam.
Small jorm: Yi inch in length, slightly more obese, without the color
rays in most cases. Common, especially in the south.
Donax califorjiicus Conrad California Donax
Santa Barbara, California, to Panama.
Plate 3ip
Up to I inch in length, narrowly pointed at both ends. Shell glossy or
oily-smooth with a tan to greenish-tan periostracum. Interior white or with