94 THE VOYAGE OF H.M.S. CHALLEN(iER. 



angle always becomes more obtuse, and on the rim the bent spicules are placed nearly 

 peripherally. Above these spicules there are straight, long, needle-shaped spicules, 

 which are arranged not very regularly in eight rows placed longitudinally with regard to 

 the pol}^ ; near the edge these are very long and form far projecting bundles, which 

 on the tentacles being folded stand up far above the polyp. Hence the po])rps have a 

 great resemblance to those of Ceratoisis, only in the latter the spicules which project 

 above the polyps stand between the bases of the tentacles, while in Acanthogorgia they 

 stand at the bases themselves. The axis is horny, fibrous, in the more slender branches 

 it is often flattened and soft, so that the branches by the upright growth of the colony 

 hang downwards. 



The following species were collected during the voyage of the Challenger : — 



1. Acanthogorgia longiflora, n. sp. (PI. XXII. fig. 1; PI. XXV. fig. 4). 



The colony is sparsely branched in one plane. In the only specimen (in which the 

 base is wanting) there arises a short stem, 1 mm. in diameter. At a height of 4 mm. 

 this divides into two tendril-like, diverging branches; These branches are 0"4 mm. 

 thick at the base and bend away from one another in an arching manner. They attain 

 a length of 100 mm. Each gives off on one side simple rod-like twigs, 45 mm. 

 in length, the first pair are at the base of the bifurcation, the next comes off in 

 the middle of the main branches, the next three at long intervals and at nearly right 

 anc^les. The branches and twigs are thin and soft and bend downwards towards the 

 base. 



The coenenchyma is very thin throughout and everywhere allows the yellowish- 

 brown axis to show through. The polyps arise from the stem and branches at wide 

 intervals from one another in alternating series. The intervals between them are 

 irreo-ular, often two on opposite sides follow close upon one another, while frequently 

 they are 2 to 3 mm. apart. At the apex of the twigs they are more thickly placed, 

 and often two to four are placed together round the stem. The apex of the twig is 

 occupied by a polyp. The polyps are very much elongated, cylindrical, and expanded at 

 the end, they are placed perpendicularly on their support but are frequently bent towards 

 the apex of the branch, like the polyps of a Primnoid. Their length reaches 8 to 10 mm., 

 their diameter 1 mm. Sometimes the lower half is thickened and swollen, so that the 

 form becomes cup-like, whilst a constriction separates the basal part from the expanded 

 tentacular part. When this is the case numerous ova are found present in the basal 

 part. The tentacles appear but slightly retractile, only the apices are bent in, and the 

 remaining portions, armed with spicules, are laid together over the mouth and form an 

 operculum, which is scarcely overtopped by the eight groups of spicules developed on 

 the margin of the polyp. The axis is altogether fibrous, horny, and in the branches and 



