Abstract:The species of the genus Enterostomula (Prolecithophora, Cylindrostomidae) belong to marine oganisms. Up to now, 3 species have been described. Species of the Cylindrostomidae family have never been reported in China. Species in the genus (E. graffi de Beauchamp, 1913)have been described for 100 years, but their gonoducts and ways of laying eggs have not been discovered yet. Since the locality, morphology and function of the genital ducts have not been confirmed for years, the classification of this genus is influenced. A species in genus Enterostomula, was collected from the coast of Shenzhen Bay in Shenzhen City (22°31′N, 113°56′E) in Guangdong Province. This study observed longitudinal, transverse and horizontal continuous paraffin sections in order to rebuild the mode pattern of its inner structure. Through the observations of its living body and ontogenesis, the epidermal patterns from the ventral side and dorsal side of the species were described in detail. The morphological study showed that most individuals had two black bands on the dorsal surface. The turbellarian had 2 pairs of dark black eyes. The turbellarian was hermaphrodite, with one testis and one ovary. The bursa seminalis was located between the ovary and the uterus. The uterus, connected with a tiny vulva, was located at the posterior end of the body. According to the characteristics above, localities of testis and vitellaria of the species matched the description of the Enterostomula graffi de Beauchamp, 1913. It was confirmed as a new recorded species, Enterostomula, Cylindrostomidae, a newly recorded family in order Prolecithophora in China. Some morphological characteristics were firstly described in this paper such as: (1) the bursa copulatrix and the female gonoduct of this species were located in their ventral side (Plate Ⅲ: 4, 5) (The bursa copulatrix, consisting of muscles, was bursiform and connected with the uterus and the female gonoduct); (2) obvious secretory glands around the female gonoduct (Plate Ⅲ: 4); (3) the foramina of the female gonoduct, the combination of the penis pore and the mouth (Plate Ⅱ: 6, 7); (4) a hemispheric nest made of mucus secreted by itself to dwell in or lay eggs; (5) no bands were found at the back of the hatched larvae and 2 obvious thick black bands were found 4 d after incubation (Plate Ⅰ: 10, 11); and (6) the bands at back of different adult individuals varied obviously, black longitudinal lines were found at their ventral side (Plate Ⅰ: 1, 8). This paper measured the “bursa seminalis” referred by Jones (1941). It had a diameter of 58μm and the wall consisting of a single layer of secretory cells was 15μm thick, thus it was considered to be a structure of the uterus (Plate Ⅲ: 3, 5, 8). In this paper, some specimens contained ova and spermatozoa in the “plasma mass of germeria” referred to Jones (1941). Thus, the bursa seminalis was considered to be the portion for fertilization (Plate Ⅲ: 1, 2).