| OCR Text |
Show 1887.] COLLECTION FROM CHRISTMAS ISLAND. 519 ovate and oblique ; outer lip the least thickened within ; columellar margin arcuate, slightly incrassated. Length 9| millim., width 5| ; aperture 5 long, 4\ broad. The oblique form, the ridgedike lines of growth, and the coarse spiral striation are the distinguishing features of this shell. LITTORINA GRANICOSTATA, sp. n. Shell ovate, acuminate above, white with a minute blackish apex, longitudinally granosely plicate and spirally ridged and sulcated ; whorls about 7, moderately convex, penultimate with about five spiral ridges ornamented with small tubercles which fall one under the other, producing longitudinal series and giving the shell a plicate appearance ; last whorl witb about thirteen ridges alternating with very fine thread-like striae, and a large broad smooth thickening around the base. Aperture roundish, brown within and Fig. 2. • Q <b i Q Littorina granicostata. finely lineated with a darker colour, with the usual basal whitish zone; outer lip crenulated at the edge, pale and ornamented with the terminations of the internal brown lineations. Columella more or less arcuate, of a dark brown colour. Length 11J millim., diam. 7 ; aperture 6 long, 3f broad. A shorter specimen is 10 in length, 6| in width. This pretty species is peculiar on account of the nodules on the spiral ridges falling one under the other, thus producing longitudinal series. The single shell from Christmas Island is rather young, but it agrees in every particular with three adult specimens without locality in Cuming's collection, from which the above description is taken. |
