the Cyclostomacea of Eastern Asia. 



465 



The following is a summary of the classification which I be- 

 lieve to be in accordance with the natural affinities of the various 

 forms mentioned, and the reasons for the adoption of which I 

 have given in the preceding pages. Believing that the several 

 characters of the generative organs, of various parts of the 

 mouth, of the tentacles, the universal presence of an operculum, 

 and the form of the mantle, taken together, far outweigh those 

 of the membranous sac which constitutes the breathing-organ, 

 I agree with those naturalists who class the order Cyclostomacea 

 with the Prosobranchiate Gasteropods, and not with the Pulmo- 

 nifera. I also believe that the characters of the animal serve 

 quite as fully to distinguish Cyclophorus and its allies from Cyclo- 

 stoma as those of the operculum do to separate either from 

 Helicina ; and that if Helicina be considered the type of a dis- 

 tinct family, Cyclostoma must take an equal rank. 



I have preserved the style of classification employed by Dr. 

 Pfeiffer. My own prepossessions would be in favour of reducing 

 the rank of the several divisions, and of ranging the subfamilies, 

 with a few additions, as genera, and the genera as subgenera ; 

 but the question is rather one of convenience than of importance. 



List of the Genera of Operculated Land- Shells inhabiting India 

 and Burma. 



I. CYCLOSTOMID^. 



Cyclotopsis. 

 Otopoma, 



II. CYCLOPHORID^. 



1. Cyclophorin^. 



Cyclophorus. 



Leptopoma. 



Lagocheilus. 



Craspedotropis. 

 Aulopoma. 

 Pterocyclos. 

 Rhiostoma. 

 Spiraculum. 



Opisthoporus. 

 Cyclotus. 

 Cyathopoma. 

 Jerdonia. 



2. Alyc^in^. 



Alycseus. 

 Dioryx. 



3. PUPININ^. 



Raphaulus. 



Streptaulus. 

 Pupina. 

 Hybocystis. 



4. Megalomastomin^. 



Megalomastoma (Copto- 



cheilus, Gould). 

 Cataulus. 



5. POMATIASIN^. 



Pomatias. 



6. DlPLOMMATININ^. 



Diplommatina. 

 Opisthostoma. 

 Clostophis. 



III. HELICINID^. 



1. Helicininje. 



Helicina. 



2. GeORISSINj3E, 



Georissa. 



IV. ACICULID^. 



Truncatella. 



