1921 1 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 scarcity 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 hirsutiuscxdus, 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. 



