222 University of California Publications in Zoology  [VoU. 23 
Biological Survey of San Francisco Bay—Cancer productus, the 
‘‘red erab,’’ 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 les off the northeast shore of Angel Island 
co 
(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) aeross 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. 
