1871.] TWO NEW SPECIES OF BRITISH HOLOTHUROIDEA. 691 



late form (fig. 2 c). The sides of the suckers contain numerous elon- 

 gated curvilinear and irregularly perforated spicules (fig. Ad), within 

 which, but perhaps only at the extremity of the sucker, are a number 

 of irregularly angular plates (figs. Ae 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 ha- 

 bitat, too, C. saxicola differs, so far as we know, from all other 

 British species of sea-cucumbers. We 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, Midler. (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 con- 

 stantly 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 abso- 

 lutely 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 LXXI. fig. 5, those of the feet in fig. b". 



Our only specimens of G. pentactes were dredged by Mr. Robert- 

 son 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. 



4. 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. 



