ALCYONAEIA. 299 



Acis alba, n. sp. Plate III, fig. 9 ; Plate V., fig. 4. 



This species is represented by a complete colony which gives the following measure- 

 ments : Height of colony, 127 millims. ; maximum width of same, 115 millims. ; 

 diameter of axis at base, 2"5 millims. 



The basal attachment consists of a flat plate-like expansion from which the main 

 stem rises. The stem reaches a height of 26 millims. and then divides into two 

 principal branches, but branching is represented between this point and the base by a 

 stumjj. The branches are given off at an angle which closely approaches a right 

 angle ; they soon turn upwards, however, and run roughly parallel to the main 

 branches. The tips of the branches and the twigs are sometimes slightly clavate. 

 The colony presents a fan-shaped appearance, due to the branching being strictly 

 confined to one plane. 



The axis is horny, greyish-black in colour in the older parts, and amber-yellow in 

 the twigs and younger portions of the colony. It is cylindrical and marked by a 

 number of irregular ridges in the lower part. 



The polyps occur on all the faces of the stem and branches, and are arranged so 

 that they give the appearance of three or four irregular lines. The verrucae are 

 small, slightly conical in shape, with a blunt tip and fairly wide base. They are 

 covered by spicules similar to those of the ccenenchyma. In several cases a verruca 

 seems to occupy the tip of a branch or twig. 



The general ccenenchyma is thin and granular in appearance, the surface appearing 

 scaly owing to the arrangement of the large flat spicules. 



The spicules appear to be in two layers, the outer consisting of thick irregularly 

 shaped flattish spicules, closely covered with rough warts, while the inner layer 

 consists of spindles often with blunt ends and more irregularly formed spicules. The 

 measurements, length by breadth in millimetres, are as follows : 



(1.) The outer layer, 0"48 X 0"23 ; 0"5 X 04 ; 0-43 X 0'29 ; 0"45 X 0"2 ; 0"2 X O'l. 



(2.) The inner layer, 0-25X0-07; 0-18X0-05; 0-22x0-08; 0'14 X 0"04 ; 0"12 X 0-04. 



The appearance of two layers may be due to the fact that the flattish spicules are 

 thicker and so stand up above the level of the other spicules. If this be so, then the 

 spicules are in one layer only. 



Towards the base of the tentacle on the aboral surface two slender converging 

 spicules are present and at their base one or more transversely placed, thus giving a 

 triangular arrangement of spicules at the base of each tentacle. 



Galls are present on several of the branches, mostly caused by cirripedes. 



The colour of the colony is greyish-white. 



Localities : Trincomalee ; deep water off Galle. 



Acis ceylonensis, n. sp. Plate VI., fig. 3. 



A small specimen, 4 centims. in height, with five branches, three of which are 

 broken. The stem measures 2 millims. in diameter at the base and is scarcely 



2 Q 2 



