1374 THE VOYAGE OF H.M.S. CHALLENGER. 



10. Alacorys octacantha, n. sp. 



Shell spiny, with deep collar stricture. Length of the three joints = 2:8:6, breadth = 3:7:7. 

 Cephalis ovate, with a short, conical horn. Thorax pear-shaped, spiny, with regular, circular pores, 

 similar to Cydadophora erinaceus, Ehrenberg (1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, 

 Taf. xviii. fig. 2). Abdomen truncate, conical, with irregular, roundish pores, and eight stout, 

 straight, thorny, divergent ribs of equal size, which are prolonged into eight free, conical, spiny 

 feet of the same length. 



Dimensions. Length of the three joints, a 0'04, b 016, c 012 ; breadth, a 0'06, b 014, c 014. 



Habitat, Central Pacific, Station 265, depth 2900 fathoms. 



Subgenus 5. Ennealacorys, Haeckel. 



Definition. Peristome armed with nine feet, three of which are primary or 

 perradial, the other six secondary or interradial. 



11. Alacorys enneacantha, n. sp. 



Shell papillate, with slight collar stricture. Length of the three joints = 2:4:8, breadth = 

 3:6:9. - Cephalis hemispherical, with a stout, conical horn of twice the length. Thorax cam- 

 panulate, with subregular, circular pores, and small, conical papillae. Thorax wider, campanulate, 

 with circular pores, and conical papillae of three times the size. Peristome with nine widely 

 divergent, little curved, conical feet, about as long as the shell. Similar to Podocyrtis vcntricosa, 

 Ehrenberg (1875, loc. cit., Taf. xvi. fig. 3), different mainly in the feet. 



Dimensions. Length of the three joints, a 0'02, I 0'04, c O'OS ; breadth, a 0'03, 5 0'06, c 0'09. 



Habitat. Central Pacific, Station 268, depth 2900 fathoms. 



12. Alacorys gigas, n. sp. 



Shell thorny, with distinct collar stricture. Length of the three joints = 1:4:2, breadth = 

 1:5:4. Cephalis ovate, with a short, conical horn of about half the length. Thorax campanulate, 

 thorny, with small, regular, circular pores, very similar to Cydadoplwra gigas, Ehrenberg (loc. cit., 

 1875, p. 68, Taf. xviii. fig. 1). Abdomen truncate, conical, smooth, with irregular, roundish pores, 

 and nine stout and straight, little divergent ribs, which are prolonged into nine cylindrical, pointed 

 feet of the same length. 



Dimensions. Length of the three joints, a O'Oo, b 0'2, c 01 ; breadth, a 0'05, b 0'25, c 0'2. 



Habitat. Fossil in Barbados. 



Subgenus 6. Polyalacorys, Haeckel. 



Definition. Peristome with numerous (ten to twenty or more) prominent feet, 

 three or four of which are primary and perradial, the others secondary and iuterradial. 



