THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 78. JUNE 1864. 



XLII. — On the Classification of the Cyclostomacea of Eastern 

 Asia. By William T. Blanford, A.R.S.M., F.G.S. 



The most generally received system of classification for the 

 various forms of operculated land-shells is, I believe, that of 

 Dr. PfeifFer, as amended in the supplement, published in 1858, 

 to his invaluable work, the * Monographia Pneumonopomorum 

 viventium.' The additions which have since been made to the 

 genera belonging to the group in most cases fall naturally into 

 the several divisions proposed. 



My own observations have been limited to the land-shells 

 inhabiting India and Burma ; but a close comparison of a lai'ge 

 number of these, together with the examination, in many genera, 

 of the animals, has induced me to believe that several slight 

 alterations and one or two important changes are requisite in 

 Dr. Pfeiffer*s classification, in order to bring it into accordance 

 with the natural affinities of the forms included. I propose, 

 therefore, in the present paper, briefly to review the various 

 admitted genera and subgenera, to propose a few additions, and 

 to add some remarks upon the distribution and mutual affinities 

 of several of the species. 



Too much stress appears to me to have been placed upon the 

 structure of the operculum. In some instances the characters 

 of genera, or even of subfamilies, mainly based upon this portion 

 of the animal, only apply to a minority of the species or genera 

 included. So long as an examination of the animal was im- 

 practicable, it was only natural that much importance should be 

 attached to the structure of the operculum ; and doubtless it is 

 in general a valuable indication of the affinities of difierent 

 species. But there are many cases in which its structure alone 

 is insufficient to establish the relations of the animal. One re- 

 markable instance may be quoted : Cyclostoma semistriatum, Sow., 

 and C. filocinctum, Bens., both have a concentric, multispiral, 



Ann. i^ Mag. N. Hist. Ser.3. Fo/.xiii. 29 



