296 University of California Publications in Zoology [Vol. 2a 



In addition to being found only on a rocky substratum, Epialtus 

 productus was always in patches of kelp, or in their immediate vicin- 

 ity : at Point Bonita, Sausalito, and east of Fort Point. Spirontocaris 

 taylori, another ' ' hard bottom ' ' species, was also taken only at locali- 

 ties characterized by an abundant growth of algae along both shores 

 of Golden Gate and in bunches of seaweed stripped from the piles 

 of the Sausalito Perry building. So far as our observations go, the 

 only other middle bay species, excepting Spirontocaris paludicola men- 

 tioned below, the distribution of which may be similarly conditioned, 

 is Spirontocaris brevirostris, for although taken near the head of Rac- 

 coon Strait on a bottom characterized simply as "stones," it was also 

 taken at the south side of Golden Gate in company with Spirontocaris 

 taylori. 



Though no doubt exercising a considerable influence on the 

 distribution of the bay species, the effect of temperature and salinity 

 on these bottom dwelling forms is much more difficult of demonstration 

 and probably less important, at least within this section, than that 

 exerted by the character of bottom. Of the species found exclusively 

 in the bay only three were taken with the tow-net, CalUanassa longi- 

 mana, Cancer antennarius and Hemigrapsus oregonensis, respectively 

 two, three, and one specimen each, the latter obviously an accident. 



Of the three middle bay species, Pandalus danae, Spirontocaris 

 paludicola, and Pinnixa littoralis, not wholly restricted to the portion 

 lying west of the line drawn above, the third was found only in the 

 predominantly muddy eastern portion of the middle bay; the first, 

 Pandalus danae, was returned but once from a "variegated mud 

 ...sand and fine gravel" bottom in this eastern portion, as com- 

 pared with thirty-two specimens from a principally coarse sand gravel 

 and stone bottom in the western portion of the middle bay; while 

 the second, Spirontocaris paludicola, was taken but twice in the 

 middle bay, once in its western portion, in the eel grass along the 

 northern shore of Angel Island, and once in its eastern portion, from 

 the algal growth in tide pools north of the Standard Oil pier, Rich- 

 mond. 



b. In lacking a straining apparatus "for removing fine particles 

 of foreign matter from its respiratory stream of water," Cancer pro- 

 ductus is ill adapted for life on more or less muddy or purely sand 

 bottoms, and although recorded from the lower bay and the easterly 

 sections of the middle bay, it was taken most frequently and abun- 

 dantly in the western middle bay, as is to be expected. Here 



