384 Mr. W. Clark on ihe Chcmnitzife. 



and will enable tbe malacologist instantly to detect an individual 

 of this genus from every other ; these characters, allowing for 

 specialty variations, are essentially the same, whether the animal 

 inhabits a shell of two or twenty volutions, whether they be 

 tumid, rounded, flat, smooth or plicated, or coiled on a discoidal 

 plane. In this genus, with two exceptions, we throw overboard 

 form and markings, with respect to generic attributes, regarding 

 all such points as only useful specialties. The first exception is 

 the constant peculiarity iu the fomi of the apex : this is never 

 absent, though it is attended by numerous modifications of in- 

 version, which however slight they may be, always prognosticate 

 that a shell with this character is inhabited by a true Cliemnitzia. 

 The second exception is the tooth or fold on the columella, 

 which, when present, however variable in figure and position, I 

 have always found to be an unerring character that the animal is 

 of Chemnitzian type ; but as it is often absent, even in the same 

 species, we have only its occasional assistance. With these views, 

 we cannot see the utility of a divisional arrangement of the 

 group; we can only acknowledge the genus Chemnitsia in its 

 comprehensive integrity for the animal we have defined. 



With respect to the apices, it is necessary to impress on the 

 student, that in all the Chcmnitzice there are numerous phases 

 of inflexion, from the most decided to the more obtusely-pointed 

 or button-shaped subreflexions. The variations arise either from 

 original configuration, or the forms become travestied from the 

 efi"ects of attrition, which will reduce the most conspicuous in- 

 verted points, of even good fresh specimens, to a button-shaped, 

 sunken, or subreflccted apex. IMalacologists may not be aware 

 that live shells, especially the littoral ones, are more liable to 

 suffer from the attrition caused by the tides and waves than 

 those of the deeper zones, and the true characters of their apices 

 are with greater difficulty appreciated from being enveloped in 

 calcareous and other extraneous deposits, the removal of which 

 often destroys the true figure of the apex, and conchologists are 

 thus misled. In many of the apices both of live and dead shells 

 the coil is rubbed through, leaving a part which becomes worn, 

 simulating a button-shaped point, which may be, and is often, 

 mistaken for that of a Rissoa by the incautious observer, leaving 

 a "•reater or less portion of the other part of the coil soldered to 

 the second volution : and microscopic aid is often required to de- 

 tect these divisions of the terminal inflexions ; but to the really 

 observant and experienced malacologist, there is a certain aspect 

 and peculiar twist at the antepenultimate bend of the inversion, 

 which detects the true conchological Chemnitzian character. The 

 only species we know of, in which any difficulty can arise by the 

 subreflexiou or bend on the second volution exhibiting a more 



