OCR Text |
Show 538 MR. K. A. SMITH ON THE GENUS ALABA. [NOV. 2, Of the species which he enumerates, A. picta, A. cornea, A. felina, A. inflata, and A. phasianella, Angas (since described), have whorls smooth and not plicate or varicose, and the labium exhibiting, in A. picta only, but tbe faintest approach to a truncation, the columella in the remaining species being rather straight, and generally blending into the labrum, which is slightly effuse at the base. Thus it will be seen that the characters assigned to the genus are not quite accurately applicable to all tbe species which have been included therein ; and therefore I would propose the following divisions, which may somewhat facilitate their identification. Those species which have the whorls strengthened with varices (generally tumid) and the columella more or less (for this character is variable) truncated, will constitute the genus Alaba proper; and those devoid of the varices and wanting the columellar truncation may form the subgenus Diala, A. Adams, I. c. 1861, viii. p. 242, and 1862, x. p. 298. The subgenus Styliferina, A. Adams, I.e. p. 299, is closely associated with the preceding group; indeed there scarcely appear characters sufficient to warrant a separation. The chief peculiarity mentioned as distinguishing this form is in the apex "vertice mucronato;" but it does not differ to any material extent from that of several of the typical species. ALABA. Whorls tumidly varicose ; columella more or less truncated; labrum thickened in the adult state. A.vibex, A. Ad.; A. tervaricosa, C. B. Ad.,- A. melanura, C. B. Ad. ; A. supralirata, Carpenter ; A. zebrina, A. Ad. ; A. leu-costicta, A. Ad. ; A. blanfordi, A. Ad.; A. puncto-striata, Gould. Subgen. DIALA. Whorls not varicose (sometimes noduled around the middle; columella straightish, not truncated ; labrum not thickened. D. lauta, A. Ad.; D. suturalis, A. Ad.; D. varia, A. Ad. ; D. sulcifera, A. Ad. ; D. picta, A. Ad. ; D. pulchra, A. Ad.; D. inibricata, A. Ad. ; D. nionile, A. Ad.; D. pagodula, A. Ad. ; D. phasianella, Angas; D. (Alaba) tenuis, Smith ; D. cornea, A. Ad.; D. simplex, Smith. Diala rufilabris, A. Ad., differs essentially from this genus in that the peristome is continuous, very much thickened everywhere, and the aperture oblique, the columella being consequently oblique also, and not more or less perpendicular as is the case in all the species in this group. Thus it will be seen that it should be removed to the genus Hydrobia. With the exception of Alaba puncto-striata, Gould, all the species above enumerated are represented in the British Museum, as are also those species described by P. P. Carpenter in tbe ' Catalogue of Mazatlan Shells.' But these, with one exception, I have purposely omitted; for the mutilated condition of the specimens is such that it is impossible to say to what genus they (when perfect) may have belonged. |