90 First Annual Report 
Fisher says of it: ‘‘This is one of the most beautiful of echinoderms, 
being characterized by many long thorny spines which are delicate 
and glassy. It ranges from Monterey Bay to Central America.”’ 
ECHINOIDEA 
Strongylocentrotus franciscanus Agassiz 
This is the large, commonly blackish purple, long spined sea 
urchin, usually found singly in the lower tide-pools. As Prof. Fisher 
remarks, it is commonly bright purple or even reddish purple. It 
is far less common than the following. 
Strongylocentrotus purpuratus (Stimpson) 
The bluish-purple gregarious sea urchin oceurs in large colonies 
in some of the lower tide-pools. One such pool at Mussel Point con- 
tains a remarkable display of these urchins. Many of them are seated 
in deep, cylindrical bores in the rock from which it is frequently 
impossible to extricate them. They apparently do not favor pools 
that are beyond the reach of low tide spray. 
Dendraster excentricus (Eschscholtz) 
“The common sand dollar of the curio store. It was formerly 
included in the genus Eehinarachnius’’ (Fisher). The shells of this 
species are occasional on the beach at Laguna. 
