Abstract: Resting cysts and vegetative cells of Ensiculifera Balech and Fragilidium Balech have never been reported in China Sea. Such kinds of cysts were collected in the East China Sea and were allowed to germinate. The cyst of Ensiculifera sp. is spherical with a diameter of 22 µm. The cyst consists of two layers and is full of greenish granules, with a bright red body inside. The cyst wall is covered with short organic spines (2 µm long). The cell of Ensiculifera sp. comprises a conical epitheca and a rounded hypotheca, with the dimension of 17.7 µm long and 12.5 µm wide on the average. The plate pattern is po, x, 4′, 3a, 7′′, 5c, 4s, 5′′′, 2′′′′. The cysts of Fragilidium mexicanum Balech are spherical with the diameter ranging from 54–60 µm. They are full of pale white granules and brown protoplasm, with a bright yellow body present. The archeopyle is spherical. The cells of F. mexicanum are 45.3 µm long and 42.8 µm wide, with the plate formula of po, 5′, 7′′, 10c, 7s, 7′′′, 2′′′′, 1P. The cyst of Fragilidium sp. is also spherical with a diameter of 45 µm, which is similar to that of F. mexicanum except that the yellow body is not present. The cells of Fragilidium sp. are 41.6 µm long and 35.3 µm wide with the plate formula of po, 5′, 7′′, 7′′′, 2′′′′, 1P. The Internal Transcribed Spacers (ITS) of Ensiculifera sp. and the small subunit (18S) rDNA of Fragilidium spp. were amplified and sequenced. Their phylogenetic positions agree with the morphological taxonomy.

Key words: Ensiculifera, Fragilidium, Fragilidium mexicanum, dinoflagellate, cyst, China Sea