THE APPLE-SNAILS OF SIAM. 21 



By actual measurement, therefore, the shell does not differ 

 materially from that of the var. subampullaeea, but it is outlines 

 rather than actual measurements that are of importance. 



Type-specimen No. ■ ° M. (Z.S.I.) 



Pachylabra begini (Morlet). 



1889. Ampullaria legini, Morlet, Journ. de Conchyl. XXXVII, 



p. 184, pi. viii, fig. 1. 

 190.1. Ampullaria legini, Pilsbry, Proc. Ac. N~at. Sci. Philadelphia, 



III, p. 189. 

 1904 Ampullaria legini, Morlet, Et. div Miss." Pavie Indo-Chine, 



III, p. 369, pi. xx, fig. 2. 

 1911. Pachylabra legini, Kobelt, op. cit., supra, p. 87, pi. xxxv, 

 fig. 4. 



Though closely allied to P- turbinis, tins species is smaller, 

 has a thicker shell and is readily distinguished by the structure of 

 its mouth. The umbilicus is also more open. The peculiarity of 

 the mouth of the shell is due to the great development and promi- 

 nent character of the peristome produced by the thickening and 

 prominence of the columellar callus and border and the thickening 

 of the lip just inside its margin. The lip is somewhat produced and 

 everted at its lower extermity. 



The surface of the shell is rather coarsely sculptured, but 

 varies in this respect. In old shells it has, even to the naked eye, a 

 reticulate appearance, at any rate on the body-whorl, owing to the 

 intersection of blunt longitudinal and spiral ridges. The latter are 

 particularly well developed. Minute spiral striae also occur, but are 

 often hard to detect. The shell seems to be peculiarly liable to 

 erosion both of the spire and of the body-whorl. 



The colour varies. In one fresh shell from the Korat district 



VOL. IV, NO. 1, 1920. 



