Five-Fingered Jack on the Oyster. 47 
confounded with them, for their arms are found to radiate from 
a clearly defined central disk, and there is no prolongation of 
their stomachs and ovaries into their interiors. The tube- 
feet pass out from the plates along the sides of the arms, 
instead of from the under surface as in the Star-fishes proper, 
and probably serve merely as a help for breathing, locomo- 
tion over the sands being effected by their long flexible arms. 
Their home is chiefly among the tangle and eel-grass, where 
their protecting covering affords them security from their 
many enemies. 
