and on some new East Indian Helicidse. 351 



west of the Ganges, although the conditions under which several 

 fine species thrive on the eastern side of the Bay of Bengal, and 

 even across the equator in Java, are equally present in Southern 

 India. Under these circumstances, it seems that the vast alluvial 

 country which stretches from the mouth of the Indus, in an im- 

 mense arc, to the Delta of the Ganges, has proved an impassable 

 barrier to this genus, which delights in a moist mountain cli- 

 mate, whether in cold or warm latitudes. 



It may not be irrelevant to notice in this place an interesting 

 fact in the geographical distribution of the terrestrial Mollusca. 

 In 1844 I established in this Journal the genus Diplommatina 

 for two small shells with a peculiar animal from the Western 

 Himalaya. Captain Hutton has a third sinistrorse species, with 

 a tubercle in the aperture, from the same quarter. I know not 

 if it be identical or not with Diplommatina Huttoni of PfeiiFer, 

 also from India, described in the unpublished Proceedings of 

 the Zoological Society for 1851. In July last I had the satis- 

 faction of detecting a fourth species among the East Australian 

 collections of Mr. Strange, by whom it had been considered to 

 be a Pupa. It is also sinistrorse, and has all the characteristics 

 of the genus, including the double peristome. I referred the 

 genus to the Carychiada, with reference to the absence of an 

 operculum, which neither Capt. Hutton, Dr. Bacon, nor myself 

 had been able to detect in the living animal. Dr. J. E. Gray, 

 in his CyclophoridcB of the British Museum, has placed Diplom- 

 matina among the operculated land-snails, and describes the oper- 

 culum, in specimens of D. folliculus from Capt. Boys' collection, 

 as being thin and shelly, with few whorls and prominent lamellae 

 on their outer edges. Mr. Strange failed to observe any oper- 

 culum in the species which he found on the promontory of Point 

 Danger, where it occurred, like its Himalayan congeners, under 

 damp decayed leaves. This is not to be wondered at when that 

 accessory piece evaded the examinations which both Capt. Hut- 

 ton and myself instituted on living specimens with the view of 

 discovering its existence, assisted, in my own case, by glasses of 

 moderate power. 



Dr. Pfeifibr, in his amended conspectus, follows Gray in con- 

 sidering Cyclostoma minus of Sowerby, a Philippine shell, to be 

 a Diplommatina ; and in referring the genus to the Cyclostomacea. 

 Neither Sowerby nor Pfeifi'er appears to have seen the operculum 

 of D. minor. Its larger size, although not so great as in Sowerby's 

 magnified figure, would show the operculum plainly if present, 

 Pfeiffer, in the ' Conchylien Cabinet,' noticed the anomalous cha- 

 racter of this species. It wants, however, the double peristome 

 of the typical species. 



Malvern, September 16, 1852. 



