beaches the red species is very abundant; the Ameri- 

 can Pacific coast species is yellow-green and grows 

 in quieter waters, often on oyster shells. Encrusting 

 practically all scallop shells in Puget Sound are yel- 

 lowish brown growths of Ectyodoryx parashka. less 

 often of Mycale adherens. North of Puget Sound and 

 into Alaska, mollusk shells, especially those of the 

 rock oyster or jingle shell, may be honeycombed to 

 the crumbling point with the tunnels of the yellow 

 boring sponge, Cliona celata, a cosmopolitan species. 

 Farther south, as in Monterey Bay, it bores in abalone 

 shells but is not so generally widespread. In the Gulf 

 of California Ricketts saw it growing, beyond tidal 



range, in its nonboring, massive form as reddish pink 

 vases several feet in diameter. On the American east 

 coast it is well known from South Carolina north- 

 ward; and it is common in European waters. The yel- 

 low massive form with wartlike vents occurs off- 

 shore; the boring type tunnels in limestone pebbles 

 and shells in shallow water. The activities of Cliona 

 are important in disintegrating the empty shells that 

 accumulate on the sea bottom, but we appreciate 

 them less when the sponge weakens the shells of edi- 

 ble clams or scallops and becomes a pest in oyster 

 beds by making oysters more vulnerable to their 

 many enemies. 



Finger sponge, with both spicules and homy matrix, from San Francisco Bay. Two tiny hermit 

 crabs explore its surface. ( Woody Williams ) 



