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Show 1892.] LAND-SHELLS OF ST. HELENA. 263 tenui prominenti in medio palati) instructa ; peristoma tenue, marginibus remotis, columellari leviter dilatato. Longit. 2 | millim., diam. 3j ; apertura lg longa, \ lata. Hab. Flagstaff Hill (E. W. Alexander). Extinct. This species has the spire more elevated and conical than the other species of Patula from the island. P. cutteri, Pfr., m ay approach it somewhat, but that species is said to have only two parietal lamellae, and two basal denticles near the columella. The present species has an additional basal denticle, and a prominent thin palatal lamella, which falls as it were between the two on the inner or parietal side of the aperture. 10. PATULA CUTTERI (Pfeiffer). Hab. Diana's Peak. Living (Pfr.). A small species, unknown to me, apparently similar in general features to the preceding, but with only four teeth within the aperture, two parietal and two basal near the columella, more narrowly umbilcated and probably more strongly sculptured. 11. PATULA POLYODON (Sowerby). (Plate XXI. figs. 8-8 c.) This is the most widely umbilicated of all the species of Patula from St. Helena, and this feature alone is sufficient to distinguish it from the rest. The whorls also, in adult shells eight to nine in number, enlarge very slowly. The stria? are fine, regular, arcuately oblique above, and slightly wavy on the last whorl. There are three parietal lirce extending far within the aperture, of which the upper and lower are nearly always double. The plicse within the outer lip are almost invariably (in adult shells) seven in number, subequi-distant, but not of equal thickness, two or three towards the columella being stouter than the rest, which are slender and extend some distance within. Diam. maj. 5j mill., min. 5, alt. 2\. Hab. Side Path, Sugarloaf Quarry, Sugarloaf Ridge (Turton). Extinct. The species to which the foregoing remarks apply is certainly the Helix alexandri of Forbes, for in the British Museum there are specimens of it presented by Mr. Alexander, who also furnished Forbes with the shells he described. Moreover the description is fairly applicable, especially that portion of it referring to the umbilicus, which is described as " maximus." It is much less certain that this is the H.polyodon of Sowerby, but as M r . Wollaston has united these species as well as H. helenensis (Forbes), Pfeiffer, it will probably be advisable to acquiesce in this decision. There are, however, certain differences in the descriptions, which seem to indicate that more than one species was described by these authors, for instance :-H. polyodon is said to consist of six striated whorls, with three parietal and five palatal lira?, and a moderate-sized umbilicus, whereas H. alexandri is described as having seven strongly striated whorls, three parietal and eight palatal lirse, and a very large umbilicus. H. helenensis is characterized as possessing eight very |
