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Show 18/1.] TWO NEW SPECIES OF BRITISH HOLOTHUROIDEA. 691 late form (fig. 2 c). The sides of the suckers contain numerous elongated curvilinear and irregularly perforated spicules (fig. 4c.), within which, but perhaps only at the extremity of the sucker, are a number of irregularly angular plates (figs. 4e and 3 / ) ; the extremity of the foot is furnished with a single central circular cribriform plate. Length from 1 to 3 inches. Colour white. Habitat. In the holes and crevices of limestone boulders between tide-marks, Westport Bay, co. Mayo, Ireland. A single specimen dredged in Birterbuy Bay, co. Galway. Cucumaria saxicola somewhat approaches in general appearance to C. lactea, but is altogether larger and more robust, and the spicules of the skin are formed on quite a different plan. In its littoral habitat, too, C. saxicola differs, so far as we know, from all other British species of sea-cucumbers. W e obtained several specimens (about half a dozen in all) amongst the shore boulders in Westport Bay; and in all cases they were very firmly attached to the rocks, following the contortions of a fissure or " worm-hole," and adhering with such tenacity as sometimes to require the aid of a knife to remove them*. CUCUMARIA PENTACTES, Miiller. (Plate LXXI. figs. 5, 6.) This species being nearly allied to the preceding, we have thought it desirable to figure the spicules, which distinguish it at once, if such a test were needed, from C. saxicola. C. pentactes is in colour dark brown or purple, is widest in the middle, and tapers much towards the hinder extremity ; it lives constantly unattached, amongst soft mud. Its skin, though to the eye and touch very much more delicate than that of C. saxicola, is seen under the microscope to be composed almost entirely of a mass of calcareous spicules, one layer superimposed on another, so as absolutely to leave no other tissue discernible. These spicules have a rounded outline, are perforated with round apertures, and round the margins, as well as in the interspaces of the perforations, are studded with large bead-like tubercles. The body-spicules are figured in Plate L X X I . fig. 5, those of the feet in fig. 6. Our only specimens of C. pentactes were dredged by Mr. Robertson in the Frith of Clyde, where it is not uncommon. EXPLANATION OF PLATES. PLATE LXXI. Fig. 1. Synapta tenera, about twice the natural size. 2, 3. Plate and anchor of the same. X 300. _! Spicules from neck of the same. 5. Spicules from skin of Cucumaria pentactes. X 210. a, seen from front; b, obliquely; c, c, laterally. 6. Foot-spicules of C. pentactes. X 105. a. The same. X 210. * The specimen from which fig. 2 (Plate LXXII.) is taken was dredged in 15 fathoms in Birterbuy Bay; its spicules are smaller and much less closely set than in those from between tide-marks in Westport Bay. |
