380 Mr. W. Clark on the Chemnitzise. 



the ' Annals.' Placed in a glass of fresh water, I found the adult 

 Tomichia creep indifferently above or under the liquid. 



The new form differs from Truncatella, as described and figured 

 by Lowe in the ' Zool. Journal/ in the tentacula, eyes, and snout ; 

 from Melania and Assiminia in the position of the eyes, and of 

 the operculum. In the true Melanite the aperture has not a 

 continuous peristome ; although the little Melaniadous genus 

 Tricida, from the mountain lakes of the Himalaya, which I de- 

 scribed in M'Clelland's ' Calcutta Journal of Natural Histoiy,' 

 has an entire aperture like that of Tomichia. 



Aix la Chapelle, March 1851. 



XKXVIII. — On the Chcranitzise. By William Clark, Esq. 

 To the Editors of the Annals of Natural History. 



Gentlemen, Norfolk Crescent, Bath, April 5, 1851. 



I REQUEST the insertion of some observations in continuation of 

 those on the Chemnitzia opalina and C. diaphana which appeai-ed 

 in the April 'Annals' for 1851. In the December 'Annals' 

 for 1850 I submitted to the attention of malacologists many un- 

 published descriptions of the animals of the Chemnitzice, but from 

 the length of the memoir, I purposely omitted for another op- 

 portunity, various important considerations, which, with the rec- 

 tifications and additions now presented, the result of a recent 

 investigation, will I think be acceptable to your malacological 

 and conchological readers, as both are frequently at a loss how 

 to determine the species of this, by far the most difficult of the 

 British gasteropodan genera, in consequence of the great num- 

 ber of spurious objects that have been deposited therein, and 

 from the obscurity in which it is still in some measure involved ; 

 notwithstanding the illuminations it has received at the hands of 

 the learned authors of the 'British Mollusca,' which have far 

 exceeded every thing that has been made known by their prede- 

 cessors. If apocryphal matters have been pressed on their atten- 

 tion by ardent communicators, these gentlemen have always re- 

 ceived them with caution, and a courteous intimation that further 

 information is required. 



The errors of the Malacology are slight, and inseparable from 

 the subject, in consequence of the rapid progress of science 

 bringing continually new facts to our knowledge ; we must 

 therefore be thankful for the present great amount of new and 

 valuable information. The expurgation from our list of the 

 spurious species is a feature of the highest moment, for if the 

 path had not been cleared, nothing but doubt and confusion 



