Out of two thousand species of _Helix_ at present known, the only one of the same type as _H. Mouhoti_ is the large _H. Brookei_, collected by Mr. Arthur Adams, in company with Sir Edward Belcher, on the mountains of Borneo, during the voyage of the ‘Samarang,’ and described by Mr. Arthur Adams in the ‘Zoology’ of that expedition. _H. Mouhoti_, of which Mr. Stevens has received a few specimens in various stages of growth, is even larger and more inflated than _H. Brookei_. In adult specimens the last whorl measures 6-1/2 inches in circumference, 3 inches in diameter, and the shell is about 2 inches high. It differs from _H. Brookei_ in being conspicuously, but not broadly, umbilicated, and in the mature lip not being in the least degree reflected at the margin. The lip itself (not the margin) is reflected at its junction with the body-whorl, partly round the umbilicus, as in the _Nanina_ form of the genus. But the most striking feature of the species is the colouring. In _H. Brookei_ the lower half of the whorls is of a uniform dark chestnut-colour; in _H. Mouhoti_ it is pure white, turned to a bright straw colour by the overlying of a shining horny epidermis, encircled immediately below the periphery by a broad, rich, purple-black band, somewhat like the bands of the large Philippine _Bulimus Reevei_, but even broader and more defined on the white ground. The region of the umbilicus is also deeply and as definitely stained with the same purple-black colour. As in _H. Brookei_, all the specimens of _H. Mouhoti_ are sinistral, or what is more commonly called reversed. _Bulimus cambojiensis._