352 Rambles Round San Francisco. [June, 
unlike the rock in color. In the last-named species the valves of 
the shell are almost entirely hidden by the thick mantle; nothing 
is visible but a row of little black bucklers along the median line 
of the animal. . 
The sculpturing of the surface of Mopalia hindsii is, like that 
of many of its relations, very delicate. Its nearest congener, 
Mopalia muscosa, and its gigantic relative, Cryptochiton stelleri, 
which when alive measures nearly a foot in length and is fully 
four inches wide, are not to be found on the peninsula of San 
Francisco, though they occur a few miles to the northward. 
As we step upon the rocks we are saluted by numerous little 
jets of water, which take their origin from soft and seemingly 
shapeless masses beneath our feet. A more careful glance at 
these shows us that they are sea-anemones, for we catch sight of 
some that are partially expanded, and on searching a little farther 
we come upon a rock pool containing numerous individuals in a 
state of complete expansion. Beautiful objects they are, bright 
green tentacles on a bright green disc, and fully four inches 
across. It is curious that this large sea-anemone, together with 
two or three smaller species common in and around the Bay of 
San Francisco are still undescribed, unless they should prove iden- 
tical with species described by Prof. Verrill from points northward 
or southward of our locality. 
Two species of sponge gathered from the under sides of the 
rocks, some limpets (Acmea), Purpura saxicola, Chlorostoma fune- 
brale, and a small Litorina make up our total catch at this spot 
before the rising tide drives us back to the cliffs, where, in 4 
recess damp with percolating water, we may capture four or five 
specimens of the rare Isopod, Lygia dilatata Stm. Everywhere 
upon the rocks, and in many places among the débris cast up by 
the tides, darting about swiftly in the sunshine and hiding in the 
crannies on our approach, we find its near relative Lygia occident- 
alis Dana; but L. dilatata is rare even in this locality, the only one 
in the neighborhood where I have met with it. 
The stream running from Mountain Lake is made use of by 
the Spring Valley Water Co., and the flume conveying its water 
to San Francisco is carried along the face of the cliffs, bridging 
the ravines to Fort Point, and forms a convenient though narrow 
_ footpath. Along this route, a little later in the season, the sloping 
portions of the cliffs will be covered with the sweet-smelling wild ~ 
