268 ; University of California Publications in Zoology  [Vou.14 
Occurrence.—At station D 5785* (2), D 5787 (1), D 5789 (2, 4). 
This species has seldom been taken north of Monterey Bay. It is 
restricted in the Survey collections to the vicinity of the Farallon 
Islands. Living specimens were dredged at two stations in 40 and 46 
fathoms on a bottom of fine dark green sand. 
Range.—The typical species, and the variety C. richardsoni (Whit- 
eaves), ranges from Queen Charlotte Islands to Lower California 
(Dall). 
VENERACEA 
VENERIDAE 
Marcia (H. and A. Adams) Fischer 
Marcia subdiaphana (Carpenter) 
Plate 19, figure 3 
Clementia subdiaphana Carpenter (1863), p. 640; (1865a), p. 56; Dall 
(1891), p. 185. 
Description.—Dall (1891) characterizes this species as follows: 
‘<The original specimens of this species were young and subdiaphanous. .. . 
The young shell is greenish, white, very thin and usually more elongated in 
proportion than the adult. Inside it (the adult shell) is of a dead chalk-white, 
with the muscular and pallial impressions polished.’’ 
Length, 5 to 20 mm. 
Occurrence.—At stations D 5785 (4,3), D 5786 (2), D 5789 (13, 4), 
D 5790 (1). 
This northern species has not hitherto been reported from this 
vicinity. Living specimens were dredged at four stations in the 
vicinity of the Farallon Islands in 33 to 46 fathoms. The bottom 
is comprised of fine dark green sand. 
In Puget Sound this species attains a size more than twice that of 
the largest specimen in our collections. In all other respects the 
forms are identical. It thus appears that this form diminishes in 
size toward the southern limit of its range. Several specimens in the 
collection of the Scripps Institution for Biological Research, obtained 
from the vicinity of the Channel Islands are in accord with this sug- 
gestion, being very diminutive in comparison to the Puget Sound 
forms. 
The fossil species Marcia oregonense Conrad is yery closely related 
to Marcia subdiaphana. Tf it is identical this form will take the name 
of the former. 
Range—Unimak Pass, Alaska to San Pedro, California. 
