AKOSTOMA 



the lens, while the lower part of the last volution^ which 

 is also convex, forms the other side. The aperture (inac- 

 curately described by Lamarck as rounded") is rather 

 semicircular and strongly toothed on both sides. I'he pe- 

 ritreme is thickened, its outer edge turned back, and its 

 inner ed^e spread over a part of the spire, for the great 

 singularity of this Genus is, that its last volution is turned 

 upwards^ so that the aperture appears upon the same plane 

 as the spire. 



Only two species of this Genus are known ; they are 

 land shells, and we are informed that they are brought 

 from the East Indies, they are both very rare and much 

 esteemed on account of their extraordinary conformation. 

 The Anostoma depressa of Lamarck, which we call A. rin^ 

 gens^ because we know no reason for changing an estab- 

 lished specific name, and it is the Helix ringens of Linne, 

 is much larger than his A. glohulosa ; its spire is also con- 

 siderably flatter, it has from three to five compressed teeth 

 in its outer lip, and when there are five, the two upper 

 ones are the smallest ; two teeth are placed upon the inner 

 lip, of which the upper one is much the larger ; this spe- 

 cies measures about an inch and an half in its greatest dia- 

 meter. The Anostoma globulosum has four teeth in its 

 outer lip and two on its inner; it has also a peculiarity, by 

 which it may readily be known, that is, a small hole pierced 

 in the upper end of the thickened peritreme, which be- 

 comes filled up by age and is then only an impressed spot. 

 In both species, a spiral brown line colours the upper edge 

 of the volutions : they are both of a pale brownish colour, 

 with spots and lines of a darker brown. 



Fig. 1. Two views of Anostoma ringens^ the upper one shewing the spire and 

 the aperture; the lower view shewing the convex under side, and 

 the last half of the last volution extending from the center to the 

 edge, to carry the aperture to the side of the spire. 

 2. Two views of Anostoma globulosum. 



