222 University of California Publications in Zoology [Vol. 23 



Biological Survey of San Francisco Bay. — Cancer productus, the 

 "red crab," like Cancer antennarius is quite closely confined to the 

 middle bay and principally that portion lying west of Alcatraz, Angel 

 Island, and the head of Raccoon Strait. Only four of the thirteen 

 middle bay stations at which this species was taken lie east of this 

 line. There is no record of it from either the upper bay or outside 

 and only three (D 5723, 5767, 5802) from the lower bay, near its 

 extreme upper end between Alameda and the Mission Rock (see 

 plate 5). 



An analysis of the various bottoms on which this species was 

 taken seems to offer a very striking explanation of its limited distribu- 

 tion within the bay, in view of the fact that Cancer productus lacks 

 the so-called "straining apparatus" for removing fine particles of 

 foreign matter from the inhalant respiratory stream of water and 

 consequently is restricted to more or less hard, ' ' rocky or gravelly bot- 

 toms." (Weymouth, 1914, p. 124.) 



Twenty-four of the total thirty-four specimens taken in connection 

 with the survey, inclusive of two seined at Sausalito, were obtained 

 within the region outlined above. The bottom throughout its extent 

 is more or less hard and is largely sand, gravel, and rock in varying 

 proportions; at one station (D 5763) the bottom for the greater part 

 was overgrown with eel-grass. Practically every Cancer productus 

 was a small or juvenile, ranging from 11 to 29 mm. in width, and it 

 is interesting to note that the only large specimen taken was dredged 

 in this sand, gravel, and rock area, in 2 to 3 fathoms, from a rocky 

 bottom consisting of angular stones of various sizes, off Yellow Bluff 

 (D 5773) just south of Sausalito. Three small specimens of the same 

 species were taken with it. Of the remaining four middle bay stations, 

 two (D 5708, 5826) lie in the stretch between Point San Quentin and 

 the Southampton Shoal light, with bottoms of "sandy mud" and 

 "fairly clean sand, with very little mud and many shell fragments" 

 respectively; one small individual was obtained at each station. One 

 of the other two stations lies off the northeast shore of Angel Island 

 (D 5718), where the bottom is "soft grey mud with great quantities 

 of worm tubes and ophiurians ' ' ; and the second was dredged in a 

 line (D 5754) across the mud flats, of slightly gritty brown mud, 

 lying between the channel east of Angel Island and the Berkeley 

 shore. From each of these stations but one small specimen was 

 returned. 



