198 Mr. W. Clark on some of the Animals of the Chemnitzise. 



the ribbed Chem. decussata and interstincta. As to the spiral 

 fold, all the Chemnitzice have it, though in many it does not 

 come into the limits of visibility ; but is that a reason to separate 

 precisely congeneric animals ? The tooth or fold, according to 

 the species, is as often absent from view in the aperture as pre- 

 sent, and it is curious that this condition is not unfrequently 

 seen in the same species. I would ask then, are the inhabitants 

 of such shells to be consigned to Chemnitzia or Odostomiat 

 Chemnitzia, even including the Odostomice and Eulimella, is not 

 so abundant in species as to supply an excuse for dividing them, 

 to assist arrangement into genera that have names, but no di- 

 stinct generic qualities. I think that in the most numerous 

 tribes, judicious grouping would be more scientific than the for- 

 mation of effete genera. 



It is necessary to offer a remark which is applicable to all the 

 MoUusca, especially to the minute ones, and peculiarly so to the 

 ChemnitzicB. Great care must be taken to distinguish between 

 bond fide specialties and those apparent ones brought on by an 

 uneasy condition of the animal, which ought always to be de- 

 scribed on the undisturbed march, when all the organs are na- 

 turally deployed, as at rest they are contracted ; and violent ex- 

 ertion, which often arises when the animal in creeping arrives at 

 the level of the water in the glass in which it is confined, or 

 meets with an impediment, has the effect of producing unnatural 

 forms : for example, the foot is often made to appear deeply 

 emarginate or hollowed out by the excessive protrusion of the 

 auricles, and the termination of the rostrum is in like manner 

 distorted by the right and left points being exserted beyond 

 nature; but all these forced positions vanish on the deliberate 

 march. A neglect of these maxims has occasionally led me into 

 errors, which will be noticed under their respective heads ; I will 

 not call them trifling, as perhaps on such, the distinctness of a 

 particular species might hinge. 



Chemnitzia acicula. 



JEulima acicula, Philippi. 

 Eulimella acicula, auct. 

 Eulimella affinis, nonnull. 



The animal inhabits a smooth, bluish white, subhyaline shell 

 of eight flat volutions, and has the reflexed apex, the constant 

 characteristic of the Chemnitzia. The mantle is even with the 

 shell, with the exception of the small fold I have alluded to 

 above ; the body does not nearly equal half the entire length 

 of the shell. The general colour of the animal throughout is 

 subpellucid frosted white, mixed with minute snowy flakes. The 



