NO. 1923. DESCRIPTIONS OF PACIFIC ALCYON ARIA— NUTTING. 51 



TRICHOPTILUM SPINOSUM, new species. 

 Plate 7, figs. 3, 3a. 



Colony 13.6 cm. long. Stem 6 cm. long, very slender, end bulb 

 hardly evident and but 1 mm. in diameter. The calyces are in two 

 very irregular rows on opposite sides of rachis and of various sizes. 

 Small (or young ?) polyps are usually found growing just above and 

 inside of the larger ones. Some of the larger calyces measure 6 mm. 

 to the ends of the spines, and have a marginal diameter of 2 mm. 

 The general shape of the calyx is a cylinder gradually expanded 

 toward the margin. The margin is armed with 8 prominent spines, 

 some of which project as much as 2 mm., each point being composed 

 of a number of needles gathered in a bundle. Other long needles form 

 8 longitudinal ridges on the calyx walls, resembling those of Pen- 

 natula. A number of smaller needles are found all over the calyx 

 walls lying criss-cross, but tending to form a horizontal band just 

 below the margin. An almost complete gradation can be found 

 between the large calyces described and apparently rudimentary 

 ones less than 1 mm. high. 



Spicules are numerous throughout the rachis. 



Zooids: Although these are present, I am unable to make out any 

 definite arrangement, or to discriminate surely between them and the 

 smallest of the rudimentary polyps, without dissecting the only 

 specimen secured. 



Color: The stalk is straw-A'ellow, deepening to an orange on the 

 end bulb. The polyps are pallid, Mdth the distal portions showing a 

 tinge of red. The spicules are all colorless. 



XocaZ%.— Station 4959; Mizimoko Shima Light, N. 23° W., 28.5 

 miles; 405-578 fathoms. 



Type-spedmen.^Cat. No. 30100, U.S.N.M. 



Genus HELICOPTILUM, new genus. 



Colony in the form of a stiff spiral; calyces biserial, each with two 

 very conspicuous spines or horns projecting from its outer margin. 



HELICOPTILUM RIGIDUM, new species. 



Plate 7, figa. 2, 2a; plate 18, fig. 5. 



Colony (incomplete) growing in an open spiral. Axis very strong and 

 stiff, quadrate in section. The largest specimen is 21 cm. in length, 

 stem missing. The rachis is flattened dorso-ventrally, lesser diam- 

 eter 2 mm., greater diameter (not including calyces), 2.7 mm. The 

 calyces are in two rows, regularly alternate, their outer margins being 

 very greatly prolonged into two conspicuous horns which often project 

 as much as 2 mm. beyond the rest of the margin. The length of 



