REPORT ON CORALS — DEEP-SEA MADREPORARIA. 159 



Colour of the animal greenish-yellow, the mouth margin white, with twelre broad 

 glistening white folds or bands, disc external to these emerald green. As far as I can 

 determine from the mutilated specimen, I believe that this coral differs from others 

 which I have examined in that in the contracted state all the tentacles are concealed, 

 the disc contracting and closing in over them as in Actinia. In the contracted animal 

 there is a sphincter-like opening in the centre of the disc, which leads to a cavity in 

 which are the tentacles, out of which again opens the mouth which is surrounded by a 

 prominent ridge. The entire outer surface of the corallum is invested by a thin lamina 

 of living tissue. Johnston observed the living British species Sphenotrochus macandreiv- 

 anus, and has given some description of it. 1 



Extreme heights of three coralla 19 mm., 17 mm., and 17 mm., respectively. Extreme 

 breadth of the calicles 20 mm. in all the specimens. Shorter diameters of the calicles 

 16 mm. to 13 mm. Extreme breadth of the abae in one specimen 3 mm. Breadth 

 at the base of the corallum between the outer edges of the alae in the above specimen, 

 16 mm. 



One perfect fresh specimen was obtained, and another which had the soft parts 

 present but had been badly crushed in the dredge, with these were two dead and partly 

 broken specimens. 



Station 192, off the Ki Islands. 129 fathoms. 



Pleurocyathus, n. gen. 



Corallum conical, attached by its side. Entirely covered by a thin plicated coloured 

 bark-like epitheca, which rises higher than the margin of the calicle. Wall of the calicle 

 very thin, except near the margin, where a zone of stereoplasma is developed, soldering 

 together the outer regions of the septa where they arise from the wall. The lower part 

 of the calicle devoid of stereoplasma or other filling. The columella composed of several 

 flattened pillars. 



The coral, for which this genus is formed, is evidently nearly allied to Duncania, 2 

 but differs in its much thinner epitheca, in the restriction of the stereoplasma to the 

 marginal region, in the absence of paliform lobes to the septa, and in the hexagonal 

 arrangement of the septa being comparatively little obscured. Lindstrom found in a 

 thin section of the apex of a Duncania six septa of the first order distinctly marked. 3 



Pleurocyathus brunneus, n. sp. (PI. II. fig. 1, a-c). 



The corallum is in the form of a short straight cone. It is attached by a broad 



adherent surface situate on one side near the apex. The external surface is covered 



with a rough brown epitheca which is extremely thin and has a pellicular appearance. 



1 British Zoophytes, 2d ejl., 1846, p. 196. 2 Pourtales, 111. Cat. Mus., Harvard, No. 8, p. 45. 



3 Actinology of the Atlantic, p. 13. 



