1921] Schmitt: The Marine Decapod Crustacea of California 297 
twenty-two specimens were taken at ten stations, all on primarily 
gravel or rock bottoms, as compared with twelve at seven stations in 
the easterly parts of the middle and lower bay, of which several had 
more or less hard bottoms, composed largely of shells, shell fragments, 
or clinkers. Aside from the searcity of favorable bottom, it is possible 
that the great fluctuations of salinity obtaining in the upper bay may 
tend to exclude Cancer productus from that division. 
c. As the bottom of the greater part of the bay is predominantly 
muddy, it is to be expected that the five bay species listed as occur- 
ring in all three divisions will show some preference for bottoms of 
that character. . 
Callianassa longimana in view of its burrowing habits would 
naturally be restricted to the softer bottoms, and it is not surprising 
that no specimens of this species were taken in the western middle 
bay. In the eastern middle bay it was dredged at nine stations, in 
the lower bay at five, and in the upper at three. 
Pagurus hirsutiusculus, although only taken in the course of shore 
collecting, from rocky shores around the middle bay, was dredged 
from more or less shelly bottoms in the predominantly muddy sections 
of the bay; once in the upper bay, four times in the lower bay and 
seven in the eastern middle bay. Of the other six stations at which 
this species was taken four were on the more or less hard sandy or 
rocky bottom of the western middle bay, and two in the eel grass 
patches around Angel Island, one in the western, the other in the 
eastern middle bay. 
Pinnixa franciscana and P. schmitti have practically the same 
range within the bay, in fact, coincide at three stations. In nearly 
every case the bottom from which they were dredged was a more or 
less sandy mud, accompanied in at least two instances by numerous 
worm tubes, the probable habitat of both species. With the exception 
of one specimen of P. franciscana taken from a bottom of ‘‘soft mud, 
with numerous worm tubes,’’ off Belvedere Point, in Richardson Bay, 
neither species was found in the western middle bay. 
Hemigrapsus oregonensis, as is well known, shows a marked 
preference for muddy bottoms, being especially abundant on mud 
flats at low tide though taken at times in more or less rocky situations 
in company with Hemigrapsus nudus. In the predominantly muddy 
lower bay an average of sixteen and eight-tenths specimens per haul 
was taken at each of sixteen stations, while in the middle and upper 
bay only one and five-tenths specimens were returned from each of 
the two hauls made in both of those divisions. 
