THE NAUTILUS. 91 
acters given previously. I have collected gravid females as early 
as Aug. 31. Glochidia were observed first on Sept. 2, so that 
the breeding probably begins toward the end of August. Dis- 
charge of glochidia has been seen from May 11 to May 24, and 
a single discharging female was found on July 5, probably ex- 
ceptionally belated. My extreme measurements of the glochidia 
are: L. 0.21 to 0.23, H. 0.27 to 0.30 mm. 
Eurynia (MicroMYA) VANUXEMENSIS (LEA). Ortmann, l. c., 
p. 530. ) 
Anatomy: see Ann. Carn. Mus. 8, 712, p. 342, and NavtIu. 
we do, p.. 65. 
Earliest date for gravid females Sept. 2; for glochidia Sept. 
17. Discharge from May 15 to May 25. 
(The species of the genus Trwncilla will be treated in a sep- 
arate paper. ) 
MODIOLUS DEMISSUS DILLWIN, IN SAN FRANCISCO BAY. 
BY G. DALLAS HANNA. 
One of the supposedly accidental introductions of animal life 
from the east to the west coast of North America with the ex- 
tensive attempts to transplant the oyster was the plicated mus- 
sel, Modiolus demissus. It was first recorded from the new loca- 
tion by Stearns in 1899 (Naurizus, XIII, p. 86) from specimens 
collected by R. N. Drake in 1894 at a point ‘‘3 miles north of 
Stanford University,’’ that is, the southern part of San Fran- 
cisco Bay. The record was repeated by the same author in 
April, 1900 (Science, n. s., XI, p. 658). 
‘‘Fine specimens’’ were again collected, apparently from the 
same colony, by Doe and Gifford, and recorded by Keep in 
April, 1901 (Navuritus, XIV, p. 115). In his ‘‘West Coast 
Shells,’’ Revised edition, p. 87, 1911, the same author states, 
‘Tt doubtless came to California with seed oysters which were 
planted in San Francisco Bay, where it may now be found in 
considerable numbers.”’ 
