1252 THE VOYAGE OF H.M.S. CHALLENGEE. 



8. Sethamphora aerostatica, Haeckel. 



Podocyrtis aerostatica, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 80, Taf. xvi. 

 fig. 4. 



Shell broad, urceolate, smooth, with sharp collar stricture. Length of the two joints = 2:6, 

 breadth = 3:8. Cephalis hemispherical, large, with few pores (broken off in fig. 4a of Ehrenberg, so 

 that the six collar pores appear). Thorax inflated, bottle-shaped, with twenty-two to twenty-four 

 smooth prominent ribs, alternating with the same number of longitudinal rows of small circular pores. 

 Mouth very small, strongly constricted, scarcely as broad as the cephalis, with three short teeth. 



Dimensions. — Cephalis 0-02 long, O'OS broad; thorax 0-06 long, 0-08 broad. 



Habitat. — Fossil in Barbados. 



Subgenus 2. Cryptocephalus, Haeckel, 1881, Prodromus, p. 430. . 



Definition. — Cephalis more or less hidden in thorax, being partly enveloped by its 

 uppermost part. 



9. Sethamphora microstoma, n. sp. (PI. 57, fig. 5). 



Cryptoprora microstoma, Haeckel, Atlas, pi. Ivii., fig. 5. 



Shell ovate, smooth, without external collar stricture. Length of the two joints = 1:6, breadth = 

 2 : 4. Cephalis flat, cap-shaped, without ribs, with small circular pores. Thorax ovate, with twenty- 

 four prominent ribs, alternating with deep longitudinal furrows, each of which contains a series of 

 about fifteen small circular pores. Mouth very small, representing a short cylindrical tube, which 

 is only one-eighth as broad as the thorax. 



Dimensions. — Cephalis 0'02 long, 004 broad ; thorax 012 long, 0-08 broad. 



Habitat. — Western Tropical Pacific, Station 220, depth 1100 fathoms. 



10. Sethamphora favosa, n. sp. (PI. 57, fig. 4). 



Cryptocephalus favosus, Haeckel, 1881, Prodromu.s, p. 430. 



Shell ovate, dimply. Length of the two joints = 1:5, breadth = 1:5. Cephalis subspherical, 

 small, completely hidden in the thickened top of the thorax (but very distinct ia the longitudinal 

 section). Thorax ovate, with twenty-five to thirty longitudinal ribs, alternating with the same number 

 of longitudinal furrows, each of which contains ten to twelve circular, hexagonally framed pores. 

 In the smooth wall of the peristome only twelve triangular ribs are visible. Mouth constricted, 

 one-third as broad as the thorax. 



Difnensions. — Cephalis 0-02 diameter ; -thorax 01 long, O'OO broad. 



Habitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms. 



