182 Records of the Indian Museum. [Vol. XIV, 



Thiele. — " Mollusca ", in Brauer's Die Susswesserjauna Deutschlands 



XIX. (Jena : 1909). 

 Troschel, F. H. — " Neue Susswasser-Conchylien aus dem, Ganges ", 



AViegmann's Arch. j. Natugesch, III, pp. 166-182 (1837). 

 Vakigny, H. de. — " Recherches sur le Nanisme experimental, etc. ", 



Journ. de U Anat. et de la Physiol., 1894, pp. 147-188. 

 Vernon, — Variation in Plants and Animals. (London : 1903). 

 Whitfield, R. — " Description of Lymnaea {Bulimaea) megasoma, etc.", 



Bull Amer. Mus'. Nat. Hist., I, pp. 29-37 (1882). 

 Woodward, B. B. — Catalogue of the British species of Pisidium in the 



Collection of the British Museum (1913). 

 ZscHOKKE, F. — Die Tiefseefauna der Seen Mitteleuropas (1911). 



NOTE ON THE PALAEONTOLOGY OF THE INLE 



MOLLUSCA. 



By E. Veedenburg, B.L., B.Sc, F.G.S., etc., Superintendent, Geological 

 Survey of India. C ommunicated by Jcind permission of the Director, 

 Geological Survey of India. 



The shells occurring in various geological formations have been 

 classified, by Dr. Annandale, according to their relative antiquity, as 

 sub-fossil and fossil. How far these two groups correspond with the 

 two divisions generally recognised by geologists in the Quaternary era, 

 the " Pleistocene " and the " Holocene " (or " sub-recent " or " recent ") 

 cannot at present be definitely settled. 



In Europe and in many other temperate regions, the termination 

 of the Glacial Period forms a convenient datum line for separating the 

 two divisions. In India, the study of the corresponding formations has 

 not yet progressed far enough to correlate them in detail with the se- 

 quence of local physical changes. 



Nevertheless, the shells which Dr. Annandale has classified as " sub- 

 fossil " may confidently be regarded as " holocene " or " sub-recent," 

 but it would be difficult at present to say for certain whether those 

 described as "fossil" should be ascribed to an earlier phase of tie 

 " holocene," or else regarded as frankly pleistocene, though the latter 

 alternative is more probable. 



Considering the great plasticity of some of the forms above de- 

 scribed, length of time need not represent a factor of primary importance 

 in the evolution of the extinct and living mutations or species under 

 consideration. Their transformations seem directly connected with 

 the changes in physical geography of the Shan plateau, and, without 

 precise information as to the geological dates of the physiographical 

 evolution of that region, we are unable to fix the exact period of the 

 correlated biological changes. 



