a 
‘ag 
1878.] Walks Round San Francisco—The Bay Shore. 507 > 
in the entrance of Oakland harbor brought it up in abundance, 
and the deep-water specimens appeared to be larger than those 
found above low tide level. Attached to the swimmerets of Gebia, 
in the spring months, will usually be found a parasitic isopodous 
crustacean, Phyllodurus abdominalis St., an odd-looking creature, 
the two sexes of which differ a good deal in form. I have never 
found more than two upon a single Gebia, and these two are 
usually male and female, sometimes there is a female alone, but as 
the male is smaller and blessed with greater locomotive powers, 
he may in those cases have been overlooked or have escaped. 
The female is literally nearly as broad as she is long, with seven 
little pairs of legs ending in hooked claws tucked under her lob- 
sided body. The male is long and slender, symmetrical, with 
the segments of the body well separated, and is very much 
smaller than his unwieldy spouse. 
Very often a small bivalve mollusc, Pythina rugifera Carpenter, 
is attached to one of the swimmerets of the larger Gebias. A 
large Nereis, about twelve inches long, gay with iridescent tints 
when placed in clear sea-water, completes the list of the silt- - 
inhabiting creatures at this spot. All the cockles found are very 
small, yet shells of the species three inches across lie upon the 
beach, and at times the Chinese colony located near the lagoon is 
in possession of many a sackful of large individuals. An “old 
inhabitant” who has been clam-digging, volunteers an explana- 
tion of this. The bed of these cockles, he says, is below low 
water, and they are only washed ashore after a storm, “It puz- 
zled him somewhat ” at first, to find out where they came from. 
A little farther on, as we leave the lagoon, the banks gradually 
rise into precipices, the beach is strewn with loose rocks, with here 
and there a larger boulder rising high among its fellows. We over 
turn a number of the smaller rocks, thinking it possible that we 
may find beneath them the large red Cancer productus, which is 
common enough in the bay, and which we have found in abund- 
ance at this season, in similar situations in Tomales bay. But — 
either we are a little too early in the season to catch them so 
high out of the water, or they do not, in this locality, venture 
beyond low-water mark. Certain it is that we have not found 
them alive, with the exception of a straggler or two on the beach — 
near San Francisco. But if, in July, we return to this spot, we 
Shall find beneath many of these stones, each in a little puddle of 
