1881.] Mya arenaria in San Francisco Bay. 363 
of Mya arenaria} rather fragile in substance and delicate in 
sculpture. 
As Dr. Newcomb considered it a new species, he described it 
as above and gave it the name of JZ. hemphillii, remarking that 
“the only species with which it can be confounded is the JZya 
precisa of Gould, which Dr. Carpenter considers as identical with 
M. truncata of the North Atlantic. A specimen of MV. arenaria, 
from Puget sound, in my collection, is quite distinct from this 
species, and, like many of the circumpolar species, is common to 
the North Pacific and North Atlantic. It is quite distinct from 
the fossil JZ. montereyi Conrad, as Iam informed by Dr. Cooper, 
who kindly made for me the comparison of this shell with Con- 
rad’s figure and description.” 
Since 1874, the date of the description, the Mya has become 
abundant, and is found for miles alongside the easterly shore of 
the bay, and is now the leading clam in the markets of San Fran- 
cisco and Oakland, superseding to a great extent the previous 
“clams,” Macerna nasuta and Tapes (or more properly Cuneus) 
staminea Conrad, in its varieties, especially diversa Sby., and the 
now dominant clam of the fish-stalls, is found exhibiting all of 
the characteristics of Mya arenaria, and is universally conceded 
to be the same as the Atlantic species. 
My friend, Dr. Newcomb, as quoted above, it will be seen, re- 
garded his Puget sound Mya as J. arenaria; which is the region 
from which Gould’s form, Mya precisa, was brought, and if re- 
lated to another form, is more likely to be a variety of the circum- 
polar ¢runcata than to be arenaria. 
one of the more recent and reliable collectors referred to in 
Carpenter’s Supplementary Report (1863) to the British Associa- 
tion, neither any collector since this date, to my knowledge, has 
verified the occurrence of MV. avenaria at any point north of San 
Francisco bay on the west coast of America. Gould was certainly 
familiar with a form so common on the New England coast; and 
though perhaps in this day and generation we hold rather broader 
views as to what constitutes a species than some of the old mas- 
“The only bivalve along the coast or in the bay of San Francisco which might be 
mistaken for or identified with Mya arenaria is Schisotherus nuttalli Conrad, which 
when mature is two or three times as large as the largest specimens of Mya. Dwarfec 
forms of the large species are found at low tide on the flats connected with Goat 
island on the east. In this species the siphons are enclosed in an external sheath, 
the same as in Mya, making what the unsophisticated call a “ long neck.” 
