THE APPLE-SNAILS OF SIAM. 3 



ignorant of the fact) a West Indian form, and (2) that the Neotro- 

 pical species differ from those of Africa and Asia in having a horny 

 instead of a calcareous operculum, and in the fact that the siphon 

 when expanded is an elongate cylindrical tube many times as long- 

 as thick, whereas that of the Oriental and African species is in the 

 same condition no longer than broad and distinctly funnel-shaped. 

 These characters seem to be of generic importance. 



Granting that these species are gtinerically distinct from the 

 American ones, and that the name Ampuilaria properly belongs 

 to the latter, recent writers adopt one of two generic 

 names for the African and Oriental species, either Pila Bolton 

 (1798) or Pachylabra Swainson (1840). Pila, as Kobelti has 

 shown, is inadmissable and I have, therefore, adopted the name 

 Pachylabra. This course leaves the family name Ampullariidae 

 intact. 



In describing the Siamese species of Pachylabra I have had 

 in my hands material from the following sources : — 



(1) The old collection of the Indian Museum, discussed in 



Nevill's "Hand List" (1884). 



(2) A fine series of shells of P. turbinis var. dalyi from 



Pitsanuloke presented to the Indian Museum some 

 years ago by Mr. H. W. Biggie of the Indian Fcrest 

 Service. 



(3) A small collectipn made by myself in the province of 



Singgora (Songkla) in 1916. 



(4) Another recently made by Mr. C. Boden Kloss in the 



Korat district and on Eoh Samesan in the Gulf of 

 Siam, and presented to the Indian Museum by him. 



(5) A series of shells and living specimens of the new 



species P. angelica sent me from Bangkok by Dr. 



Malcolm Smith in July, 1919. 



I have to thank those who have provided much of this 



valuable material, and also Dr. Baini Prashad of the Bengal Fishery 



Department, who has sketched the radulae figured in this paper 



1 Kobelt, Fam. Ampullariidae in Martini and Chemnitz's Conch. - 

 Cab., p. 44 (1911). See also Dall, Journ. Conch. (London) II. p. 50 (1904). 



VOL. IV, NO. b 1920, 



