摘要
螺蛳属(Margarya)是云南省各湖泊特产的腹足类,属田螺科(Viviparidae),其分类问题已有详细的研究(张玺、齐钟彦,1949)。在研究滇池西岸两种螺蛳,即螺蛳(M.melanoides Nevill) 和牟氏螺蛳〔M.monodi (Dautzenberg et Fischer)〕的变异问题(张玺、夏武平,1949)时,曾发现螺蛳从滇池西岸北部水域向南到牟氏螺蛳分布地区海口之间,壳的形态有向牟氏螺蛳接近的趋势。这一现象的产生,是两个种的发展有趋同的趋势,还是两个种的地理分离还不够完善呢?当时未能探讨。近年来又有机会到昆明,注意到湖滨土层中存有大量的螺壳,而且两个种都有,故又收集了一些材料,从亚化石上再探讨一下此类问题。探讨中确知上两螺种在过去是同域分布,以后逐渐地理分离,同时还发现了一些其他有关演化的问题。
It was revealed in 1949 that in the water along the west coast of Kunming Lake, two snails, Margarya melanoides and M. monodi, were distributed separately, the first in the north and the latter in the south part of the lake;and some shell morphological characters of the first species are tending to approach those of M. monodi, from north part southward. Now basing on subfossil materials, this problem has been discussed again from the evolutionary and historical point of view. Three snail groups were recognized in the specimens collected. ( 1 ) Liren snail group, two species, M. melanoides and M. carinata existed.(2) Xihua snail group, two species, M. melanoides and M. tchangsii existed. (3) Lungwangmiao-Huiwan snail group, four species, M. melanoides, M. monodi, M. yini and M. elongata existed. The last group might be descended from the Xihua snail group;and the Liren group might be independent from the others. The gee-graphical separation of the two living snails, M. melanoides and M. monodi, was found tn occur in rather recent time, i.e.within 500 years. A sympalric speciali m of the snails was suggested and a new snail was described. Description of Margarya tchangsii Xia, sp. nov. Shell conical, thick and solid, body whirl un-swelled, spire very high, apex abtuse, suture deep. Whorls, 6, each whorl increasing gradually downward in width. Ramp-like area is rather prominent. On each spiral whorl there are 3 spiral keels, on which nodules are regularly scattered. The body whorl with 7 keels, on which nodules are also scattered, but sometimes inconspicious in the part near the apertute. Aperture, oval-shaped. Umbilicus, small and covered. Measurements, see Table 6 This species is distinguished from M. monodi by its slender shell and the body wherl being n A swelled. It is different from M. yini by its shell being not so(?)long, and the nodules on the keel being more regular;besides, the nodules are searsely combined together into a horizontal band as in M. yini. Therefore it is considered as a new form.
作者
夏武平
Xia Wuping(Northwest Plateau Institute of Biology,Academia Sinica and Department of Biology;Beijing Normal University)
