61 



Acanthomuricea ramosa, n. g. et sp. Plate V. figs. 1,4, and 8 ; 



Plate IX. fig. 5. 



This new genus is established for two interesting specimens in which the axis 

 is horny, solid in the older parts, but hollow and very soft in the younger portions. 

 The colony is branched in one plane, but small twigs may arise at right angles to 

 the plane of branching. The branching is irregular, but often alternate The 

 coenenchyma is thin, like rough bark, with imbricating scales. The verrucas occur 

 on all sides of the axis, either closely or at moderate intervals, usually leaving the 

 dorsal surface free in the older portions of the stem and branches. The tentacular 

 portion of the retracted polyp forms a prominent conical operculum. The verrucse 

 are prominent, upright, almost cylindrical, with the spicules arranged in rows (some- 

 times slightly irregular) ending in eight points. The spicules of the verrucfe are 

 irregular plates with a projecting spine, irregular discs with divaricate edges, elon- 

 gated forms with broad bases, and a few irregularly branched rods. Those of the 

 general coenenchyma are irregular discs, flat bars, and spindles with a large foliaceous 

 expansion about the middle of one side. 



This genus seems to be related to FJacogorgia, but differs from it in the 

 thinness of the coenenchyma, in the size of the verrucas, and in the tentacular 

 operculum. 



More detailed Description. 



The genus is represented by a large greyish-black, upright, fan-shaped colony, 

 27 cms. in height, with a maximum width of 23 cms. 



The base consists of a flat spreading stolon-like portion which surrounds a 

 fragment of PleiirocoraUium. Almost at its origin the main stem gives off" a 

 branch at right angles. The branching is in one plane, and for the most j^art 

 roughly alternate, though this is broken through, either by two branches alternating 

 with one, or by an approximation to the dichotomous type. At the tip of a 

 branch there are two or three verrucse. 



The thin basal portion is remarkable in having single polyps scattered over its 

 surface, and in givinsf off" a small branch from the under surface which lies in 

 the same plane as the main colony, but has its apex directed in the opposite 

 direction. 



The axis is horny, 575 mm. in diameter near the base. It is solid in the 

 lower part, but soon becomes hollow. At first the central tube is of small diameter, 

 but it gradually increases in size till in the younger branches and twigs the walls 

 become so thin that a slight touch compresses the tube and puts the walls in 

 contact with one another. The axis is easily broken, and has its surface, at 

 least in the main stem and branches, marked by a number of longitudinal 

 striations. 



