AMPULLARIA globosa, 

 Round Apple Snail. 



Generic Chauacteu. — See PI. 103. 



Specific Character. 



A, testa globosa, Icevissimd, olivaceu ; spird depressd ; apertura- 

 margine crasso, fulvo, sulcato ; umbilico parvo, contracto, jiixta 

 basin posito ; operculo testaceo. 



Shell globose, very smooth, olive ; spire depressed ; margin of the 

 aperture thick, fulvous, grooved ; umbilicus small, contracted, 

 placed near the base ; operculum shelly. 



Helix AmpuUacea. xar. Gmelin, p. 3626. no. 43. Chemnitz, 9 tab. 

 128./g-. 1133. 1134. p. 10,5. 



This is the most common of the two shells of this genus, 

 which have their mouths closed by a shelly operculum. It 

 is well described by Chemnitz, and his figures are very 

 tolerable ; yet, like all the authors of that period, he con- 

 sidered it as a variety of Helix ampiiUacea. From all these 

 supposed varieties it is, nevertheless, quite distinct; the 

 spire is more depressed than that of any other species, and 

 the umbilicus is placed near the bottom of the inner lip : the 

 whole shell is very smooth, and, although generally of a 

 uniform yellowish olive colour, is sometimes marked by 

 narrow bands of purple brown. The margin of the outer 

 lip is slightly reflected, and the colour, beneath the epi- 

 dermis, almost white. It is a native of the rivers of India. 



From the remarks on this genus, made at Plate 103, the 

 fact of their opercula being either shelly or horny, is suffi- 

 ciently established. These formations, however, there is 

 every reason to suppose, may generally be detected by the 

 following indications. In such species as have a shelly 

 operculum, the margin of the aperture is thickened all round, 

 and has a parallel internal groove for its reception : the pro- 

 bable use of this groove I have detailed elsewhere. On the 

 other hand, in those species which are known to have horny 

 opercula, this margin and groove do not exist; and that part 

 of the shell which is between the top of the aperture and the 



PI. 119. 



