1330 THE VOYAGE OF H.M.S. CHALLENGER. 



shorter, with three concave basal edges and irregular, polygonal pores. Feet from the girdle 

 strongly divergent, nearly straight. 



Dimensions. Length of the three joints, a 0'02, b 0'08, c 006 ; breadth, a 0'03, b 01, c 012. 



Habitat. Central Pacific, Station 263 to 274, depth 2350 to 2925 fathoms. 



4. Pterocanium contiguum, Ehrenberg. 



Pterocanium contiguum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. xvii. fig. 7. 



Shell three-sided pyramidal, smooth. Length of the three joints =1 : 3 : 2, breadth = 1 : 4: 6. 

 Cephalis small, subspherical, with a large conical horn three times the length. Thorax and 

 abdomen with small, regular, circular pores of equal size, densely crowded together, with 

 thin bars. Abdomen shorter, with three concave basal edges. Feet very thick, straight, from 

 the girdle strongly divergent. 



Dimensions. Length of the three joints, a O'OIS, b 0'05, c 0'025 ; breadth a 0'02, b 0'08, c 012. 



Habitat. Fossil in Barbados. 



5. Pterocanium pyramis, n. sp. (PL 68, fig. 7). 



Shell three-sided pyramidal, smooth. Length of .the three joints =1:4:3, breadth = 2 : 4:6, 

 Cephalis hemispherical, with a conical horn of the same length. Thorax campanulate, with fifteen 

 to twenty prominent longitudinal ribs, separating as many rows of regular, circular pores. Abdomen 

 shorter, with three concave basal bays, and irregular, roundish pores. Feet very strong, pyramidal, 

 straight, gradually divergent from the girdle. 



Dimensions. Length of the three joints, a 0'025, b 0'08, c 0'06 ; breadth, a 0'04, b 0'08, c 012. 



Habitat. Central Pacific, Station 266, depth 2750 fathoms. 



6. Pterocanium virgineum, n. sp. (PI. 73, fig. 6). 



Shell nearly three-sided pyramidal, smooth. Length of the three joints = 1:4:8, breadth 

 2:6:9. Cephalis hemispherical, with a conical straight horn three times the length. Thorax 

 campanulate, with three slight swellings between the three knee-shaped ribs, and with regular 

 circular pores. Abdomen longer, with three concave basal bays, and with very small and 

 numerous pores (much smaller than those of the thorax). At both sides of the three prominent 

 abdominal crests, two rows of larger, nearly square pores occur. Feet slender, nearly straight, 

 divergent. 



Dimensions. Length of the three joints, a 015, b O06, c 012 ; breadth, a 0'03, b 0'09, c 014. 



Habitat. Central Pacific, Station 271, depth 2425 fathoms. 



7. Pterocanium prcetextum, Haeckel. 



Lychnocanium prcetextum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. lierlin, p. 297, Taf. x. 



fig. 2. 



Shell nearly three-sided prismatic, smooth. Length of the three joints = 1 : 2 : 1, breadth = 

 1:4:4. Cephalis subspherical, with a straight, conical horn of three times the length. Thorax 



