中国小豆螺属一新种描述

DESCRIPTION OF A NEW SPECIES OF BYTHINELLA FROM CHINA

小豆螺是一种微小的淡水螺类，属于 螺科(Hydrobiidae)，小豆螺属(Bythinella)。该属首次报道于欧洲(Ehrmann，1933)，后曾在日本发现，近年又在我国湖南(刘月英等，1979)、湖北(康在彬，1983)等省发现。其中有些种类是并殖吸虫(Paragonimus)的第一中间宿主，因此，引起了寄生虫学家和医学贝类学家的极大关注。

In the present paper a, new species of the genus Bythinclla belonging to the family Hydrobiidae is described. The specimens of the new species were collected in 1979—1983 from Wufenig County of Hubei Province. The types are deposited in the Department of Parasitology, Hubei Medical College.Bythinella lii, sp. nov. (Figs.1—4) Description: Shell ovate-conoidal, minute, thin, translucent, dull white; smooth except for the very weak incremental lines. Whorls 4 in number, each of which well convex with a deeply constricted suture. Apex small but obtuse. Spire short and conic. Body whorl very large and inflated, the base of which strongly rounded, and descending to the aperture; it measures about two-thirds the length of the shell. Aperture large, roundly ovate; peristome continuous, simple, with a brownish margin; outer lip thin, roundly curved, inner lip more or less straight, slightly reflected outwards, and its middle portion attached to the body whorl. Umbilicus narrow but distinct. Operculum elliptical, rounded at both ends, 0.789 mm in length and 0.408 mm in breadth, corneous, thin, semitransparent, light yellow, paucispiral with excentric nucleus.The animal is usually light yellow. The single tentacle on each side of the head in life is long and slender, slight swollen at the base and pointed at the end. In alcoholic specimens the tentacle is thick and flat, and its length is always longer than the snout. The small black eyes are situated at the dorsal side of the base of the tentacles. The proboscis is wide and short, and slightly bilobed in front where the mouth is located. The mantle is dull white, translucent, and its edge is smooth, without processes of any kind. The verge of the male is simple, slender and light yellow, and is coiled up at the back of neck near, the right, and its end is bluntly pointed. The radula is band-form, 0.678 mm in length and 0.62 mm in breadth. The central tooth has 7 denticles on the free edge, of which the median is the larger. It also has two pairs of basals; its formula, therefore, is The lateral tooth has a large denticle and 3 lesser ones on the inside of this and 4 on the outside. The inner marginal bears 25 denticles and the outer 18.Holotype: Length 2.4 mm, breadth 1.43 mm; length of aperture 1.01 mm, breadth of aperture 0.84 mm; length of body whorl 1.63 mm; length of spire 0.77 mm; collected on July 15, 1979 at Lon gqiao Village, Wantan District, Wufeng County, Hubei Province, China. Paratypes: Length 2—2.43 mm (average 2.268 mm), breadth 1.28—1.44 mm (average 1.356 mm); length of aperture 0.85—1.02 mm (average 0.978 mm), breadth of aperture 0.71—0.86 mm (average 0.782 mm); length of body whorl 1.41—1.64 mm (average 1.55 mm); length of spire 0.59—0.78 mm (average 0.712 mm); collected from the above-mentioned locality; 15 July 1979; 14 January 1983. Habitat: The minute snails of the new species live in the small mountain ditches where the altitude is approximately 1100 meters above sea level. The sides of the ditches are overgrown with weeds. The bottom is full of sand and small stones. The water is little, cool and slowly-flowing. The snails were attached to the underside and flank of the. small stones, with the majorty to the underside.Etymology: This new species is named in honor of Prof. F. C. Li, the famous Chinese anatomist, one of the early workers of Oncomelania in China.