BIVALVES (MOLLUSCA) OF TUNG-TING LAKE AND ITS SURROUNDING WATERS, HUNAN PROVINCE, CHINA

Tung-Ting Lake, one of the great lakes of China, is located in the northern part of Hunan Province, communicating with the Yangtsekiang at its middle reach. It receives waters chiefly from the Siang River (湘江), Tse River (资水), Yuan River (沅水) and Li River (澧水) from south and west and flows into the Yangtsekiang at Cheng-Ling-Chi (城陵矶). Specimens were collected from the different regions of the lake and its surrounding waters in May, 1956. April to May, 1962 and March, 1963. From the materials, 47 species (see Tab. 3) belonging to 4 families (Mytilidae, Unionidae, Cor-biculidae and Sphaeriidae) and 16 genera, including one new species and one new subspecies, were determined. Among them, 24 species (marked each with an asterisk in Tab. 3) are recorded for the first time from this region, 35 species are found to be endemic to China, while the remaining 12 species are widely distributed in Asia. The characteristics of this fauna may be summariaed in the following points:1. The species Lamprotula leai (Gray), Lamprotula caveata (Heude), Lamprotula rochechouarti (Heude), Hyriopsis cumingi (Lea), Unio douglasiae (Gray), Arconaia lanceolata (Lea), Cuneopsis pisciculus (Heude), and Anodonta woodiana woodiana (Lea) are found to be predominant in this region.2. The number of species and individuals are found to be more abundant in the lake than in the rivers, ponds and other water bodies.3. While the majority of the species are found to be common in the different water bodies, there arc certain other species which are found only in waters with different sediments at the bottom.4. In the lake region, Unioidae is gradually reduced in the number of species as well as of individuals from south northwards and becomes very scarce in the northwestern part of the lake.Descriptions of new species and subspecies1. Acuticosta trisulcata triangula, subsp. nov.Localities; Changteh (常德), Yiyang (益阳), bottom sand-mud or mud-sand.Shell small, scalene triangulate, moderately thick, solid, subinflated, very inequilateral; beaks scarcely projected and full; anterior end widely rounded; posterior end narrowly subtruncate; post-dorsal margin oblique; base line almost straight. Beak region with three conspicuous subconcentric furrows; epidermis yellow-fuscous; left and right valves similar in form, each provided with a pseudocardinal tooth but right one being more conical than the left one; right valve with only one lateral tooth and the left with two lateral ones; anterior muscle scar more deeply impressed than the posterior one; nacre ashy-white, no beak cavity.Holotype: Length 29mm, height 19mm, diameter 13mm; locality: Yiyang (益阳), collected on April 20, 1962, by Lin Chen-tao and Wang Yo-hsien.Paratype: Length 27mm, height 19mm, diameter 13mm; locality: Yiyang, col- lected on April 20, 1962.Holorype and pacatype are deposited in the Institute of Zoology, Academia Sinica, PekingComparison: By examination of the specimens so far obtained, the characteristics of this new subspecies arc found to be very constant, except for size variations. This new subspecies may be readily distinguished from Acuticosta trisulcata trisulcata (Hcude) by characters, as shown in table 1:2. Anodonta angula, sp. nov.Localities: Ponds in Hengyang (衡阳), Chansha (长沙) and Mi-Lo (汨罗), muddy bottom. 25 specimens collected in various water bodies of these places.Shell large, thin and friable, sub-elliptical; beaks placed at the middle of dorsal margin, somewhat inflated but not porjected; dorsal margin of shell short and quite straight, its anterior and posterior ends similarly angulated; post-dorsal margin obliquely straight, post-dorsal angle above the level of the median line, anterior margin rounded, base line arched; epidermis yellow-green, well-shined, with very fine and faint radiant lines.Holotype: Length 97 mm, height 59 mm, diameter 37 mm, locality: Hengyang, collected on April 8, 1962, by Lin Chen-tao and Wang Yo-hsien.Paratype: Length 89mm, height 53mm, diameter 34mm; locality: Hengyang, collected on April 8, 1962.Holotypc and paratype are deposi