[N.S., XIX, 1923.] Zool. Results of Expedition to Yunnan. 401 
Limnaea yunnanensis * Nevill .. W. Yunnan, as far 
east as Erh-hai. 
Fam. Planorbidae. 
Gyraulus longios,* sp. nov. .. Upper Mekong. 
Several points in this list are noteworthy. Firstly, we 
notice the complete absence of Ampullariidae, which are 
abundant in many parts of Burma and Siam but do not occur 
in any part of China, where they are apparently replaced by 
gigantic Viviparidae of the genus Lecythoconcha. Secondly, 
the absence of Melaniidae from Western Yunnan is peculiar. 
Those which occur in the eastern and central parts of the 
province are not related to Burmese forms. e most inter- 
esting fact, however, is the occurrence of the apparently 
endemic and highly peculiar lacustrine genera Delavaya, Para- 
pyrgula, Paraprososthenia and Fenouilia in the lakes of the 
Province. A peculiar feature of those molluscs is their close 
resemblance to certain tertiary forms from Central Europe. ! 
A similar resemblance has been noticed between the Vivi- 
paridae of Yunnan‘and these of the Plaistacian beds of central 
and eastern Europe and the Levant. This resemblance is 
certainly due, as I have demonstrated elsewhere,? not to a 
common ancestry but to convergent evolution, and I am of 
the opinion that the similarity between the other lacustrine 
gastropods of the Jakes of Yunnan and those of tertiary basins 
m Europe is probably due to the same cause Before dis- 
cussing the matter fully, however, it will be necessary for me 
9° make a more detailed study of the tertiary molluscs. and 
this is not possible at present in Calcutta. 
Family RISSOIDAE. 
Subfamily LirHoGLYPHINAE. 
Genus Lithoglyphus Hartmann. 
Although this genus has been confused with the indigenous 
genus Fenowilia, at least one true species (L. liliputanus 
Gredler) has already been described from China. The radula’° 
has been figured by Dr. Baini Prashad and myself. I have 
here to describe a new species closely allied to the type-species 
of the genus, so far as can be seen from the shell alone. 
Lithoglyphus taliensis, sp. nov. 
The shell is of comparatively large size and has 34 whorls. 
The body-whorl is comparatively shallow and very oblique, 


| See Neumayr, NV. Jahrb. /. Min. Geol. u. Pal., I, p. 21 (1883). 
* Annandale, Proc. Roy. Soc. (B) XCVI, pp. 60-76 (1924). 
* Ree. Ind. Mus., XVI, p. 416, Fig. Ib (1919). 
