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



spindles, about 0'33 mm. in length and 0'03 mm. in diameter, and are thickly covered 

 with short, sharp spines. The walls of the polyp also exhibit eight longitudinal bundles 

 of thickly disposed spicules. At the base of the tentacles the spicules are arranged in a 

 circle and forqa a sort of collar. Thence they are continued into the tentacles, in which 

 they lie obliquely and close together. They become gradually shorter towards the tips of 

 the tentacles. 



The gastral cavity of the polyp is sunk deep into the relatively thick coenen- 

 chyma. 



The colour in spirit of the basal membrane and calyx is milk-white, and that of the 

 retractile portion yellow. 



Habitat— Station 320, lat. 37° 14' S., long. 53° 52' W.; bottom, green sand ; depth, 

 600 fathoms. 



Sympodium armatum, n. sp. (PL XLIII. figs. 11, 12). 



From a thin membrane which covers a Gorgonoid (Dasygorgia), the polyps arise in 

 groups, at wide intervals. One can distinguish a more or less expanded calyx portion 

 with a broad base, and a tentacular portion which is not completely retractile. The 

 calyx wall bears but indistinct longitudinal striae. In each group five to seven 

 individuals are usually distinguishable, arising close to one another but separated from 

 the next group by a wide interval, over which the naked basal membrane extends. Both 

 the membrane and the calyx walls appear somewhat rough owing to the spinose spicules 

 which are embedded in them. 



The calyces are not rigid, they measure 4 to 4*5 mm. in breadth at their base, they narrow 

 rapidly towards the oral region, and are from 3 to 4 mm. high. The anterior portion of the 

 polyp is only partially retractile, so that the tentacles which are folded together over the 

 oral disc cannot be drawn into the calyx, and being provided with spicules form a quasi- 

 operculum. The base of the gastral cavity is sunk into the ccenenchyma of the basal 

 membrane. In the groups each gastral cavity is separate down to the base. 



Both the basal membrane and the calyces are beset with large rough spicules, wliich 

 lie in the calyces in eight longitudinal bundles, but in the membrane they are irregularly 

 disposed. They consist of straight or curved spindles, beset with sharp spines. By the 

 thickening of one extremity they frequently become club-shaped. Their length and 

 breadth vary respectively as follows: — 07 to 0-04, O'S to 0-04, 0-41 to 0-042, O'SS to 

 0-04, 0-5 to 0-04, 0-41 to 0-042, 0-38 to O'OS, 0-3 to 0-03 mm. Even the retractile 

 oesophageal portion is covered with fine spindle-shaped spicules. 



Under the tentacles, curved spicules, measuring O'SS to 0-05 mm., form a broad 

 annular collar, which in retracted polyps forms the margin of the calyx. 



