Two new (2-phenylethyl)amine alkaloids, convolutamines F and G, and a dibromohydroxy-oxindole alkaloid, convolutamydine E, have been isolated from the butan-1-ol soluble material of the Floridian marine bryozoan Amathia convoluta. Their structures were elucidated on the basis of spectroscopic data. Convolutamine F exhibited activity against KB, KB/VJ-300, and U937 cells. This compound also exhibited the inhibitory effects for cell division of fertilized sea urchin eggs.