144 THE VOYAGE OF H.M.S. CHALLENGER. 



rather small size, with a few small, simple double-spindles, and rarely small, irregular 

 crosses." To this may be added that in the structure of the axis there is a general 

 resemblance to that of Plexaurella. The following two species come from Japan. 



Euplexcmra jnnnata, n. sp. (PL XXXIII. fig. 5). 



The colony arises from a broad, irregular, membranous base, which spreads over the 

 .surfaces of rocks, stones, &c. In well-developed specimens, the main axis reaches a 

 height of 3 dm. ; being slightly flattened at its base, where it measures from 5 to 6 mm. 

 in diameter. Two branches are given off at a height of 5 mm., and these give origin 

 to a second and third series of Ijranches, which are all given oS in the one plane ; the 

 primary branches reach a length of 2 "5 dm., other lateral branches are given off at 

 intervals of from 6 to 10 mm. and are about 3 mm. in diameter, tapering from this to 

 2 and 1 mm., so that the whole colony assumes a broad, flattened, fan-shaped form. 



On cross section the axis is seen to consist of a central hollow or somewhat calcareous 

 portion, 5 mm. in diameter, which is surrounded by a horny layer, 1 mm. in thickness ; 

 this is infiltrated with calcareous particles, which want, however, the symmetrical 

 arrangement which is seen in Plexaurella. In the outer layer the nutrient canals run. 



The polyps are scattered in irregular spirals over both the axis and the branches ; 

 they are completely retractile within the thickness of the coenenchyma. When the 

 polyps are quite withdrawn, the walls of the coenenchyma close in over them so that 

 there is but little trace of the polyp cavities, but when these cavities are left partially 

 open, they are somewhat oval in form. 



The coenenchyma is dense and granular. The spicules of the polyps are small 

 flattened needles, toothed on their edges, mixed with some quadriradiate forms ; the , 

 spicules in the tentacles are minute curved needles, those of the coenenchyma are 

 small warty spindles with a few tri- and quadri-radiate forms. 



The spicules measure 0-06-0-02 ; 0-1-0-04 ; 0-2-0-04 ; 0'12-0-04 ; 0-16-0-04 ; O'l- 

 0-04; 0-1-0-08; 0-1-0-02 ; O'OS-O-OG mm. 



The colour in spirits is a light brown. 



It is possible that this may be the Plexaura olivacea, Lamx.,^ described as " Plexaura 

 ramosissima ; ramis sparsis vel subpinnatis ; cortice olivacea ; cellulis sparsis distantibus. 

 Indes orientales." 



Habitat. — Stations 233 and 233a, Kobe, Japan, May 17, 19, 1875 ; depths, 8 and 50 

 fathoms. 



Euplexavra jyarciclados, n. sp. (PI. XXXIII. fig. 6). 



In this species the colony arises by a much-divided base which spreads over and 

 clings to small shells and pebbles. 



1 Hist, des Polyp, flexibles, p. 431, pi. xvi. (Hist. Nat. des Coralliaires, vol. i. p. 156). 



