4 DR. NELSON ANNANDALE ON 



and has given me other assistance. The drawings and photographs, 

 here reproduced, have been prepared by the artists of the Zoological 

 Survey of India. 



The Zoological Survey of India would be very grateful for 

 further specimens from any part of Siam, as they would be of great 

 assistance in the survey of the freshwater molluscs of the Indian 

 Empire that we are at present undertaking. Living snails will 

 travel safely in a dry condition to Calcutta by post, as those sent 

 me by Dr. Malcolm Smith have proved. 



Pachylabra Swainson. 



1911. Pachylabra, Kobelt, Fam. Ampullariidae in Maitini and 



Chemnitz's Gonch. Cab., p. 44. 



In this genus are included all the normally right-handed 

 species of Ampullariidae that have a calcareous operculum. It is 

 necessary to insert the word "normally", because in certain species 

 ( e, g. the common Indian P. globosa ) abnormal shells occur 

 ( very rarely ) that have a left-handed spiral. Information 

 is not available as to the anatomy of such aberrant individuals, but in 

 the African genus Meladomus, in which a left-handed spiral is a 

 normal generic character, the shell is said to be hypertrophic and 

 the anatomy of the animal is not reversed. 



The range of the genus is strictly tropical. In India it does 

 not extend into the Punjab, though it embraces the whole of the 

 plains of the Gangetic system and the greater part of South India. 

 Generally speaking it may be defined as consisting of the Ethiopian 

 and Oriental Regions, including Madagascar, with the exception of 

 desert and mountainous areas. In Siam at least seven species are 

 found. In " Etudes di verses " of the Mission Pa vie to Indo-China 

 (Vol III, 1904, p. 425) Fischer and Dautzenberg give the following 

 particulars of species recoi'ded from Siam : — 



P. borneensis (Philippi) from Bangkok & Chengmai 



? P. celebensis (Quoy & Gaimard) „ " Siam " 

 ? P. conica. (Gray) „ „ 



P. globosa (Swainson) „ (The marshes of the Menam 



near Bangkok) 



JOURN- NAT, IJIST. SOC. SJ.' .M 



