OCR Text |
Show 1894.] LAND-SHELLS PROM THE SAMUI ISLANDS. . 151 Fam. STENOGYRIDJE. 14. O P E AS GRACILE, Plutt. 15. OPEAS FILIFORME, sp. nov. (Plate XVI. fig. 11.) T. rimata, gracillime turrita, tenuis, subtiliter et maxime confertim striatula, nitens, pellucida, albida ; spira sensim attenuata, apice obtusulo. Anfr. 7|, convexiusculi, lente accrescentes, sutura impressa discreti. Apertura modice obliqua, anguste acuminato-ovalis ; peristoma rectum, acutum, margine columellari incrassa-tulo refiexo. Alt. 5-5, diam. 1*5 millim. I do not know any similar small and slender species of Opeas ; the comparatively great number of whorls show that it is adult. Pam. PUPID^E. 16. VERTIGO (STAURODON) MORELETI, Brown. Subsp. nov. SAMUIANA. Differs from the Borneo and the Philippine-Island type (v. Jahresb. Senckenb. nat. Ges. 1890, p. 252) in the slightly more contracted shell and in the somewhat deeper groove behind the outer peristome. 17. HYPSELOSTOMA TRANSITANS, sp. nov. (Plate XVI. figs. 12, 13.) T. umbilicata, turbinata, oblique striatula, fusca. Anfr. 4, convexi, spiram conicam apice papillari formantes; ultimus paullum distortus, antice non ascendens, breviter solutus et porrectus, perip>heriam crista sat prominente, altera minore ad suturam ductus, basi subgibber, circa umbilicum compressus. Apertura parum obliqua, rotundato-tetragona; peristoma continuum, tenue, expansum, hand reflexum. Lamella parietalis validiuscula, antice bifida, dentibus 2 in margine externo, 1 in basi et 1 in columella oppositis. Diam. 2-75, alt. 2-66 millim. This peculiar shell presents an especial interest inasmuch as it forms a decided transition from Hypselostoma to the Indian and Chinese Boysidia, Ancey, of which Pupa hunanensis, Gredl., is the type. As 1 have mentioned in the description of Hypselostoma hungerfordianum (P. Z. S. 1891, p. 338), the genus appears to be but an extreme development of the Boysidia type. Boysidia strophostoma, Mdff., of South China, shows already a slight distortion and detachment of the last whorl, which in the Samui species is much less developed than in the other forms of the genus. There can be no doubt, however, that it belongs to Hypselostoma, with which it has the peculiar quadrangular shape of the last whorl and the dentition of the aperture in common. H. cr.ssei, Mor., of Tongkin seems to connect it with the other Malayan species. |