of the Pacific Shores of North America. 523 
open, and presents a succession of inaccessible, perpendic- 
ular, rocky cliffs alternating with barren beaches of sand, 
all being completely exposed to the action of the breakers, 
which roll in upon them with the concentrated force of the 
storms of a wide and unbroken ocean. There is a want of 
variety in station, and a paucity of inlets, bays and islands, 
in the protected nooks of which such animals as we are 
now to consider usually find shelter. Extensive dredging 
operations would no doubt bring to light many species in 
places where the nature of the bottom is favorable, but 
the submarine zone in which the depth of water is not too 
great for the existence of animal life, is narrow; since, as 
we might judge from the mountainous character of the 
shores, the sea-bottom dips far beyond the reach of the 
Ordinary sounding-line, in close proximity with the land. 
There are but two important inlets on the coast, and of 
these Puget Sound is without doubt the best locality for 
researches among the marine invertebrata. The Bay of 
San Francisco, from the admixture with its waters of the 
turbid flood of two large rivers, and the smallness of the 
gate which admits to it the clear water of the ocean, is 
nearly barren of animal life except at its entrance. Ata 
former epoch, and one geologically speaking quite recent, 
the sea had a much freer sweep through the bay. On its 
Shores I have often observed extensive superficial deposits 
of shells, of the same species that now live on the coast, 
(Mytiti, Ostrec, etc.) lying in a horizontal stratum at a slight 
elevation above the present high-water mark. These are 
Particularly abundant beneath the soil in the valleys of 
Petaluma and Sonoma, extending thence toward the sea 
at Bodega; and here perhaps an ancient gate existed. 
Another opening may have been situated at the southern 
“xtremity, through what is now the Valley of Santa Clara. 
A preponderance of Asteriade will be noticed among 
the Echinodermata now to be described. The restricted 
Snus Asterias (Asteracanthion, Müll. et Trosch.) is par- 
