1318 THE VOYAGE OF H.M.S. CHALLENGER. 



wings, which are longer than the shell, fenestrated at the base, and S-shaped, curved. Abdomen 

 barrel-shaped, with wide, truncate mouth. Pores irregular, roundish, of very different sizes. 



Dimensions. Length of the three joints, a 0'02, b 0'08, c 0'08 ; breadth, a 0'03, b 016, c 012. 



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



7. Pterocorys hirundo, n. sp. (PI. 71, fig. 4). 



Shell slender, ovate, with two deep strictures. Length of the three joints = 1:4:4, 

 breadth = 2 : 5 : 5. Cephalis hemispherical, with a large pyramidal horn longer than the half 

 shell. Thorax conical, spiny, prolonged above the lumbar girdle into three slender, triangular, 

 prismatic wings, which are about as long as the shell, and slightly curved downwards, with lower 

 convexity. Abdomen inflated, with wide, truncate mouth, Pores irregular, roundish, of very 

 different sizes. 



Dimensions. Length of the three joints, a 0'03, b 0'08, c 0'08 ; breadth, a 0'04, b 01, c 01. 



Habitat. Central Pacific, Station 272, depth '2600 fathoms. 



8. Pterocorys barbadensis, Haeckel. 



Pterocanium barbadense, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 82, 



Taf. xvii. fig. 6. 

 Pterocyrtidium barbadense, Biitschli, 1882, Zeitschr. f. wiss. Zool., Bd. xxxvi., Taf. xxxiii. 



fig. 29, a, b. 



Shell slender, smooth, with two slight strictures. Length of the three joints =1 : 3 : 4, 

 breadth = 2:4:4. Cephalis hemispherical, with a stout pyramidal horn of twice the length. 

 Thorax campanulate-conical, in the lower half with three divergent, angular wings, which are 

 slightly curved downwards, and as long as the thorax. Abdomen cylindrical, with wide, truncate 

 mouth. Pores small, subregular, circular. 



Dimensions. Length of the three joints, a 0'02, b 0'05, c 0'07 ; breadth, a 0'04 ; b 0'07, c 0'07. 



Habitat. Fossil in Barbados. 



9. Pterocorys apis, Haeckel. 



Pterocodon apis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 82, Taf. xix. fig. 3. 



Shell slender, smooth, with two distinct strictures. Length of the three joints = 1:2:6, 

 breadth = 2:3:4. Cephali s hemispherical, with a curved, conical horn of three times the length. 

 Thorax very small, with three nearly horizontal, conical wings, which are slightly curved down- 

 wards, and twice as long as the thorax. Abdomen cylindrical, three times as long as the thorax, 

 with wide, truncate mouth. Pores small, subregular, circular. Differs from all other species 

 in the very small size of the thorax ; the abdomen is broken off in Ehrenberg's figure. 



Dimensions. Length of the three joints, a 015, b 0'02, c 0'06 ; breadth, a 0'02, b 0'03, c 0'04. 



Habitat. Cosmopolitan ; Atlantic, Pacific, many stations ; also fossil in Barbados. 



