180 SHELLS AND SHELL-FISH. PART I. 



The variations in the forms of the species are thus seen 

 to be a primary character in all these groups^ whether 

 we look to the primary divisions or genera^ or to their 

 sub-genera. It is singular how very closely some of 

 the little shells of Ferussac's Partula put on^ as it Avere, 

 the very colours of the Achatinellce, which they are to 

 represent ; and even the " slight prominence on the 

 columella" is analogous to the thickened fold-like ter- 

 mination of that part in some Aohatince: both^ more- 

 over, are chiefly found in the Pacific islands ; and both, 

 by having the broadest lips of their respective congeners, 

 aptly represent the Cyclostomce. 



(168.) The sub-genus Auricula is no less interesting 

 than the last ; because, although few in species, its re- 

 lations are unusually complicated. We shall first notice 

 those types upon which there can be few or no doubts, 

 and then advert to such as are questionable. The know- 

 ledge which Guilding's drawings of the Auricula un- 

 dulata* has given us of the animal, clearly shows its 

 close approximation to that of Bulimus hcemastomus, also 

 figured by the same exquisite artist. This fact goes to es- 

 tablish Auricula as a division of the Bulimi, and we have 

 to consider what other shells showaclose similarity to this. 

 The species we may thus select, are the Auricula Dombey- 

 ana, Auris-Leporis, Sileni, and JBovina ; and the whole 

 group may be described as shells with the aperture rather 

 larger than the spire, the whorls of the latter few and 

 produced, the pillar one or two plaited, and the outer 

 lip (except in Dombeyana +) thickened and reflected on 

 he external edge. This latter definition would exclude 

 Auricula midce, and those other dubious terrestrial spe- 

 cies whose spire, although much shorter, is composed of 

 more whorls. We suspect, indeed, that these latter shells 

 are nearly allied (through Pedipes and Melampus^ to 

 Tournatella ; in which case both them and the sub-genus 

 Scarabus must be removed from the Helicidce, a.i\d placed 



* Plecocheilus iinilulatiis Guikling, Zool. 111. Cd Series, pi. 10'3. 

 t I apprelierui, however, that in perfectly adult specimens, this species 

 has a similar outer lip to A. Silent. 



