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



The polyps are situated in rows on both sides of the stem and its branches, leaving 

 the whole central portion of these, both front and back, quite free from polyps. Both 

 polyps and tentacles are retractile, the former are lodged within well-marked verrucse ; 

 the tentacles are first infolded and then completely withdrawn. The verrucje seem to be 

 more prominent towards the summit of the branches, but in some instances it seems 

 evident that when the polyps are completely retracted, the walls of the verrucae can 

 contract over them, so as to leave the verrucas not very prominent ; the verrucae measure 

 at their base about I '5 to 3 mm. in diameter. The apices of the stem and branches do 

 not end in polyps. New polyps arise alongside of and between the old polyps. The 

 nutrient canals surround the horny axis as in Plexaura. 



The axis is flattened, horny, with a central calcareous core ; it is very flexible and 

 tough. In certain portions, on section, calcareous deposits are seen, but these have not 

 the symmetry of those to be met with in Plexaurella. 



There is a circlet of curved spiny spindles around the base of the tentacles, and smaller 

 spindles, but straight, clothe the dorsal surface of each tentacle ; very minute needle-like 

 spicules are found in the tentacles. The spicules measure, the large spindles with rough 

 spines, 0-6-0-1 ; O-S-Ol ; 0-4-0-1 ; O-.S-O'OS ; those with few spines, 0-2-0-02 ; 0-1-0-08 ; 

 0-1-0-02; 0-08-0-02; and the stellate spicules measure 0-2-0-1; 0-14-0-2; 0-12-0-12; 

 0'l-0"08 ; 0"l-0"06. Most of the spicules are of an amber colour. 



The colour in spirits is that of a dark brick-red. 



Habitat. — Banda, in 14 fathoms. 



Genus Callistephanus, n. gen. 



Axis horny, circular, with a calcareous central portion, and in the older portions 

 calcareous particles interspersed ; branched, branches arising in the one plane, mostly at 

 right angles to the stem or to one another. Nutrient canals surround the central axis. 



Polyps very prominent, the tentacles and bodies retractile within dome-shaped 

 verrucse, and arising for the most part alternately from the sides of the stem and 

 branches. 



The ccenenchyma is thick, granular. The spicules of the coenenchyma are spiny 

 spindles, clubs, and half-sided warty clubs ; those of the base of the polyps are needle- 

 shaped. 



Verrill ' describes a new genus of Gorgonid for a small delicate coral, pure white 

 in spirits, with rather prominent calycles in two alternating rows. This species, Steno- 

 gorgia casta, externally resembles Thesea and Eunicella, but in the former the 

 coenenchyma has a superficial layer of scales, and in the latter it has a regular external 

 covering of club-shaped spicules standing perpendicularly to the axis. In Swift ia, which 



■ Bull. Mus. Comp. ZooL, vol. li. p. 29. 



