22 Mr. W. Clark on rare British Gasteropodous Mollusca. 



IV. — On some of the rarer British Gasteropodous Mollusca. 

 By William Clark, Esq. 



To the Editors of the Annals of Natural History. 



Gentlemen, Exmouth, Devon, June 1852. 



I BEG the favour of you to record the discovery of some of the 

 rarer British Gasteropodan Mollusca, which have hitherto either 

 escaped the researches of naturalists, or been mentioned so im- 

 perfectly as to afford little assistance to science. During the 

 present May and June I have met with the animals of the Chem- 

 nitzia fenestrata, Ch. scalaris, Ch. clathrata, Ch. acicula ; and seen 

 many specimens of the Ch. elegantissima and Ch. pusilla, men- 

 tioned in the 8th vol. of the 'Annals,^ N. S. p. 112, which con- 

 firm the distinctness of the two, agreeably to M. Philippi. I 

 have likewise reviewed all the Chemnitzia of my two memoirs in 

 the ' Annals,^ N. S. vol. vi. p. 451, and vol. viii. p. 108, and ex- 

 amined others of the animals of this genus, which with me in- 

 cludes the Odostomice and Eulimellce of authors, and 1 can confi- 

 dently state that they do not offer the slightest generic variation ; 

 indeed some of them scarcely present, from their similitude, suf- 

 ficient specific characters. 



I cannot doubt but the genus Chemnitzia will ultimately com- 

 prise these species and some of those of Aclis. I consider the 

 Chemnitzian family one of the most interesting and classic of our 

 indigena ; nature has stamped it with unmistakeable distinction. 

 I think that a disseverance of its integrity by the distribution of 

 any of its species in other genera, can only be looked on as a 

 disruption of natural affinities. 



With regard to the Rissoce, I have examined the animal of 

 R. proxima, which has long been a desideratum, to settle the 

 doubts respecting it and Montagu's R. vitrea; and also the 

 R. punctura and R. reticulata of that author : this last discovery 

 solves another difficulty. The R. striata, R. semistriata, R. cos- 

 tata and R. soluta have also been observed. On my return to 

 Bath, I will arrange the minutes of all that are now men- 

 tioned. As these animals have long been sought for, I regret 

 that I cannot at once send the descriptive notes ; but I am so 

 immersed in the examination and acquirement of these difficult 

 minute objects, that I am obliged to solicit this postponement; 

 and I hope in the interim still further to diminish the number 

 of our rarer desiderata. 



I am. Gentlemen, your most obedient servant, 



William Clark. 

 P.S. I may mention that I have taken here a second example 



