15. Genus—OCTOMERIS. Pl. [20.]
OCTOMERIS. G. B. Sowerby. Zoological Journal, vol. 2, p. 244, July, 1825.
Compartments eight: radii with their edges crenated: basis membranous.
Distribution, Cape of Good Hope; Philippine Archipelago.
The two species of this genus differ considerably in external appearance, though not in essential character. Both, as the name expresses, have eight compartments: the carino-lateral pair are rather narrower than the lateral. The basis is membranous. The radii are narrow, and are distinctly crenated on both sides of the sutures with the teeth neatly interlocking; but these teeth can hardly be distinguished in the large, corroded specimens of [O. angulosa]. The crenated structure of the radii is identical with that described under [Chthamalus dentatus] and [Hembeli]; if, indeed, we were to add carino-lateral compartments to the shells of these two species, they would belong to [Octomeris]. I have seen only a few specimens of either species of [Octomeris], and none preserved in spirits; and therefore I know nothing of the anatomy of the softer parts: I was not able to make out distinctly any branchiæ. The cirri differ considerably in the two species, in nearly the same way as in the two species of [Chamæsipho]. In the structure of the second pair of cirri, and in the tendency of the basal margin of the parietes to form bay-like indentations, [Octomeris angulosa] shows some special affinity to [Chamæsipho scutelliformis]. Under [Pachylasma], I stated that that genus was closely related to [Octomeris]; and I have just alluded to the close affinity of the latter to the division of the genus [Chthamalus], which has crenated radii.
1. [OCTOMERIS] ANGULOSA. Pl. [20], fig. [2 a]-[2 b].
OCTOMERIS ANGULOSA. G. B. Sowerby. Zoological Journal, vol. 2, July, 1825. And Genera of Recent and Fossil Shells, Plate.
-------- STUTCHBURII. J. E. Gray. Annals of Philosophy, new series, vol. 10, August, 1825.