834 MR JAMES J. SIMPSON 



Cactogorgia alciformis, n. sp. (figs. 4, 5, 6a, 66, 6c). 



This species is represented by a very rigid colony of an orange-brown colour, 

 45 millims. in height, 40 millims. in breadth, and about 10 millims. in thickness (tig. 5). 

 It has a short sterile trunk from which three large lobes arise approximately in one 

 plane. These lobes have the characteristic appearance of the previous two species ; 

 they are markedly flattened and bear the polyps mainly on the margin, but by a torsion 

 in the plane of flattening the latter appear as if clustered terminally. In addition to 

 the three large lobes there are also three smaller groups of polyps. 



The whole colony is very stiff and rigid, and the central canal system is almost 

 obscured by the densely packed spinose spindles. The surface, when viewed with a lens, 

 is bright and glistening, and shows innumerable short, thick warty spindles interlocking 

 in all directions. 



The polyps occur chiefly on the margin ; they are supported by truncated conical 

 verrucse about 2*5 millims. in height and 2 millims. in diameter at the top. The verruca? 

 are directed towards the upper portion of the colony, and are longer on the outer margin ; 

 they are built up mainly of longitudinally arranged spicules. 



The anthocodise (fig. 7) are completely retractile ; when fully expanded they are 4"5 

 millims. in length and 2 millims. in diameter. The " crown and points" arrangement of 

 the spicules is not so definite as in the other species. On the stomodceal region the spicules 

 are disposed circumferentially in 10-14 interlocking rows. In the upper portion, however, 

 they gradually pass into an "en chevron " arrangement, so that eventually they form 

 eight triangular groups, each consisting of 10-15 spindles with no very regular disposi- 

 tion. The diameter of the upper portion is slightly greater than that of the lower. 



The tentacles, which are infolded over the oral opening, are 2 millims. in length and 

 0'75 millim. in breadth. On the aboral surface there is a distinct spiculation pattern. 

 The triangular part corresponding to the main axis is closely covered with scale-like 

 spicules arranged in pairs forming a V ', these become smaller towards the tip, but the 

 same arrangement is distinguishable throughout. The same pattern is continued into 

 the pinnules. 



The spicules of the trunk are short, thick spindles densely covered with rough warts. 

 Those of the anthocodise are longer and narrower ; they are thickly beset with spines or 

 small warts. On the tentacles the sj)icules have an almost scale-like appearance, with 

 slightly irregular edges ; some are constricted at the middle. The following are some 

 of the measurements of length and breadth in millimetres : — 



A. Stalk and trunk— I -6 x 0'45 ; V2 x 0"4 ; lx0'3; 6 x O'lo (fig. 9a). 



B. Anthocodise— 1 -2 x 0'1 ; l'l x 0*1 ; 08 x '075 ; 05 x 0'05 (fig. 9b). 



C. Tentacles — 



(a) Scale-like— 0-12 x 0'02 ; 0-06 x 0'02 ; 0'05 x 0'02 (fig. 9c). 



(b) „ with constriction— 0-08 x 0-03 ; 0'04 x 0D2 (fig. 9c). 

 Locality. — Andamans. 



