I concur with Mr. Dillwyn in believing that this shell is the _Helix glauca_ of Linnaeus; but, as it is now removed to another genus, I think no real advantage would result from continuing its original specific name; particularly as the identity may be questioned by others, without a chance of the question ever being settled: the adoption of the specific names given to species slightly or incorrectly described by the older naturalists, inevitably tends to increase the original obscurity, in all cases where the point cannot be cleared up. _A. effusa_ may be distinguished from all others by the columella being nearly obsolete; this part existing only in the two terminal whorls of the spire. This species therefore forms a transition to the _Planorbes_: there is a variety, with narrower stripes, double the size of that here figured. * * * * * AMPULLARIA luteostoma, _Yellow-mouthed Apple Snail._ * * * * * _A. testa globosa, striata, olivacea, lineis remotis fuscis fasciata; spira levata, apice acuto; apertura effusa intus marginata; umbilico magno._ Shell globose, striated, olive, with remote transverse brown lines, spire elevated, the tip acute; aperture wide, within margined; umbilicus large. * * * * * The umbilicus of this shell is not so deep as the last, but is larger than in any other known species; the columella is likewise perfect, and the aperture is wider and more oblique than in _A. effusa_. * * * * * Pl. 158 [Illustration] PINNA bullata, (_var._) _Rufous Pinna._ * * * * * GENERIC CHARACTER. _Testa longitudinalis, cuneiformis, aequivalvis, apice hians, basi acuta; natibus rectis. Cardo lateralis, edentulus. Ligamentum marginale, lineare, praelongum subinternum._--Lamarck, _Sys._ vol. vi. p. i. p. 129. Shell longitudinal, wedge-shaped, equivalve, the valves gaping; the umbones straight, pointed. Hinge lateral, without teeth. Ligament marginal, linear, very long, subinternal. Generic Types. _Pinnae rudis._ _Pectinata._ _Muricata._ Linn. Pennant, &c. * * * * * SPECIFIC CHARACTER. _P. testa tenui, pellucida, rufa, aequilatera, striis remotis, sulcatis, transversim squamiferis, subspinosis; marginibus lateralibus rectis; margine inferiore oblique truncato._ Shell thin, pellucid, rufous, equilateral, with remote sulcated striae, crossed by transverse scales and obtuse spines; lateral margins straight; inferior margin obliquely truncate. P. bullata. _Gmelin_, _p._ 3367. _Gualt._ _tab._ 79. _f._ c. _Chemnitz._ 8. _tab._ 87. _f._ 769. _Knorr_, 2. 23. _f._ 1. P. marginata. _Lam. Sys._ 6. _p._ 132. 7. * * * * *