scy·phis·to·ma 
(sī-fĭstə-mə)
(sī-fĭstə-mə)n. pl. scy·phis·to·mae (-mē) or scy·phis·to·mas
A larva of a scyphozoan, consisting of a very small sessile polyp that successively splits off free-swimming medusas.
[New Latin : Greek skuphos, cup + Greek stoma, mouth.]