These relative distinctions may be comprised in a few words; they rest principally on the spire, which in _C. generalis_ has the upper half much lengthened, slender, and acuminated: in _C. maldivus_ the spire is thick and much shorter: the whorls in both these species are quite plain, and nearly flat: the spire of _C. cinctus_ resembles the last in form, but is deeply concave and striated. These characters are, I think, very satisfactory as specific distinctions. On the other hand, some attention to these shells lately, has convinced me that many of the species formed both by Bruguiere and Lamarck should be more correctly considered as varieties; inasmuch as their specific distinctions rest, for the most part, on _colour_ alone: this appears, indeed, to be the leading character selected by these eminent conchologists, and to which, therefore, they have attached the greatest importance. From this opinion, however, I completely dissent; on the principle, that no character which is variable can, with any consistency, be made use of to express permanent distinctions, when not supported by peculiarity of formation or sculpture. The great art in framing the description of a species consists in singling out those characters alone which are most permanent, and exist in every variety of that species; for, when once a character is found to be variable, it no longer becomes a distinction by which a species can be recognised. I consider, therefore, formation and sculpture as the only certain characters of species, and that variation of colour should alone distinguish varieties. It is therefore not surprising that the specific characters given by MM. Bruguiere and Lamarck, and resting principally on the colours of these shells, are frequently obscure, and always long; two inevitable evils attending every attempt to describe minutely the colour, form, and disposition of the markings of shells. In justice, however, to these great naturalists, it should be observed, that in this attempt they have done that best which no writer has ever done well. The spire of _C. generalis_ is generally spotted, and the white band on the margin of the body whorl, more or less crossed by broad waved stripes of a dark brown. It is an inhabitant of many parts of the Indian Ocean. * * * * * Pl. 119 [Illustration] AMPULLARIA globosa, _Round Apple Snail._ * * * * * GENERIC CHARACTER.--See Pl. 103. * * * * * SPECIFIC CHARACTER. _A. testa globosa, laevissima, olivacea; spira depressa; aperturae margine crasso, fulvo, sulcato; umbilico parvo, contracto, juxta basin posito; operculo testaceo._ Shell globose, very smooth, olive; spire depressed; margin of the aperture thick, fulvous, grooved; umbilicus small, contracted, placed near the base; operculum shelly.