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



polyps are bright yellow. The cells are small, verruciform, and covered by small fusiform 

 spicula, branches slender, axis light yellowish-brown, horn-like." 



The colour and the condition of the spicules in our specimen agree with this 

 diagnosis, but as more exact data are wanting the identity must remain doubtful. 



The general habit of the colony quite recalls that of the preceding species. In form 

 it is fan-shaped, ramified in one plane, divisible into a main stem and stout branches, 

 on which the terminal twigs exhibit a pinnate arrangement. The height of the entire 

 colony is 200 mm., and the greatest horizontal expansion is 250 mm. The main stem 

 arises from a flat, encrusting base and ascends in an undulating manner. The bends of 

 the stem take place in the plane of ramification and obliquely to it, and appear to 

 be independent of the development of the branches. Numerous larger and smaller 

 branches come off from both sides, commencing at a height of 22 mm. and following one 

 another at intervals of 4 to 7 mm.; they stand off from the stem at angles of 45°, 55°, to 

 60°, the latter being the angle especially in the case of the smaller branches. The large 

 branches have almost the same thickness as the main stem and attain the same length. 

 They give off again, like the main stem, lateral branches and smaller twigs from both 

 sides, and this ramification may take place in the same manner up to the formation of 

 twigs of the fifth order. The terminal twigs are short, and flattened in the plane of 

 ramification in the same manner as the branches and secondary branches. They are 

 blunt or somewhat thickened at the ends. Short, unbranched twigs arise from the main 

 stem, as well as from the branches, in addition to the larger, branched ones. All the 

 branches and twigs remain of nearly the same thickness from the base upwards. 



Length of the main stem 155 mm.; thickness of the same at the base 3 mm.; thick- 

 ness in the middle 3 "5 mm. Length of a large branch 150 mm.; thickness of a large 

 branch 3 mm. Length of a terminal twig 17 mm.; thickness of the same 1'5 mm. 



The polyps occur on the stem, branches, and twigs, especially on one surface of the 

 colony, while the other surface shows only the coenenchyma. But even on the polyp- 

 bearing surface the polyps are more abundantly developed on the margins, so that even 

 here it is possible to distinguish a central region, in which the polyps are less abundant. 

 On the terminal twigs they are placed quite laterally, usually at distances of 2 mm. 

 Each polyp has a truncated, conical calyx, whose diameter at the base is 1 mm., while 

 its height is 0"9 to 1 mm. 



The calyces usually project at right angles from the coenenchyma, but towards the 

 ends of the branches and twigs they are directed obliquely towards the apex. The 

 tentacular operculum, distinguished by its bright yellow colour, forms a low cone within 

 the calyx. At the apices of the twigs there are two divergent polyps and between them 

 a short, rounded process. 



The spicules of the coenenchyma form a simple layer of large, longitudinally 

 arranged spindles, which are usually curved and often S-shaped. Frequently the 



