_Unio fragilis_ is principally distinguished by the cardinal teeth: those in the right valves are 2; short, obtuse, and nearly obsolete, more resembling tubercles, than the crenated or striated teeth of this genus. The left valve has one tooth rather sharper. In young shells the ligamental margin is nearly straight, and its extremity somewhat angulated; but old shells lose these appearances, and become perfectly oval. In both stages of growth the shell is very thin, convex, and the inside (near the umbones) purple. The slight development of the cardinal teeth brings this shell nearer to the genus _Anodon_, than any other _Unio_ which I have seen. It inhabits the rivers of North America, and was sent to me by Professor Rafinesque. * * * * * Pl. 172 [Illustration] AMPULLARIA reflexa, _Purple Apple Snail._ * * * * * GENERIC CHARACTER.--See Pl. 103. * * * * * SPECIFIC CHARACTER. _A. testa ovato-globosa, laevi; spira ventricosa, obtusa, sub epidermide purpurea; apertura nigro-purpurascente; labio exteriore tenui, margine reflexo._ Shell ovate-globose, smooth; spire ventricose, obtuse; beneath the epidermis, purple; aperture blackish purple; outer lip thin, the margin reflected. _Knorr_, _vol._ 5. _pl._ 5. _f._ 2. (uncoated.) Ampullaria reflexa. _Swainson, in Tilloch's Ph. Mag._ _vol._ 61. _p._ 377. * * * * * The only record that I can find (in the works of the old writers) for this Ampullaria, is the figure by Knorr above quoted; it is obviously drawn from an uncoated specimen, although I have seen instances, where the blackish purple on the spire was so intense, as to obscure the thin epidermis which covered it. The peculiar character of the species, and in which it differs from all others, is in the outer margin of the lip; which is thin, rather spread out, and slightly reflected; the form of the shell resembles _A. fasciata_, but the spire, instead of being pointed, is obtuse; the umbilicus, likewise, is smaller and more concealed. From the absence of a groove round the aperture, I conclude the operculum is horny. The size varies; perfect shells are in my possession much smaller than the figure, and I have seen others much larger, and with the aperture more chesnut than purple. I am not acquainted with its locality. * * * * * Pl. 173 [Illustration] GALLINULA ruficollis, _var._ _Black-bellied Gallinule_ _var._ * * * * * GENERIC CHARACTER. _Gallinula._ Briss. Cuv. Tem. Lath. _Fulica_, _Rallus_. Linn. _Crex._ Illiger.