1300 THE VOYAGE OF H.M.S. CHALLENGER. 



Thorax inflate, subspherical, truncate, with large, irregular, roundish pores, four to six times as large 

 as those of the cephalis. Mouth constricted, flat, one-third as broad as the thorax. 



Dimensions. Cephalis 0'03 long, 0'04 broad; thorax 015 long, 018 broad. 



Habitat. Fossil in Barbados. 



5. Sethocyrtis subacuta, Haeckel. 



Eucyrtidium subacutum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, Taf. vii. 



fig. 18. 



Shell smooth, pear-shaped, with sharp collar stricture. Length of the two joints = 1:4, 

 breadth = 1:3. Cephalis subspherical, with small, irregular pores and a rudimentary horn of half 

 the length. Thorax ovate, with large, subregular, hexagonal pores and thin bars between them. 

 Mouth constricted, flat, half as broad as the thorax, without prominent peristome. 



Dimensions. Cephalis 0'02 long, 0'02 broad ; thorax 0'08 long, O'OG broad. 



Habitat. Philippine Sea, depth 3300 fathoms (Ehrenberg). 



6. Sethocyrtis pleuracantha, Haeckel. 



Eucyrtidium pleuracantkum, Elirenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 293, 



Taf. vii. fig. 21. 



Shell smooth, bottle-shaped, with distinct collar stricture. Length of the two joints = 2:4 

 breadth = 1:3. Cephalis slenderly ovate, with an excentrie pyramidal horn of the- same length. 

 Thorax inflate, ovate, with irregular, roundish pores and thin bars between them. Mouth con- 

 stricted, flat, half as broad as the thorax, without prominent peristome. 



Dimensions. Cephalis 0'04 long, 0'02 broad; thorax 0'08'long, 0'06 broad. 



Habitat. Tropical Pacific, Stations 200, 225, 266, 274, &c,, at various depths. 



7. Sethocyrtis agamemnonis, n. sp. (PI. 62, figs. 11, a, I). 



Shell pear-shaped, rough, with sharp collar stricture. Length of the two joints = 2 : 10, 

 breadth = 3 : 8. Cephalis subspherical, with very small pores and a small, pyramidal horn of 

 half the length. Thorax inflate, ovate ; in the uppermost part (beyond the collar stricture) with 

 a ring of six to nine very large roundish pores, which are twice to four times as broad as the 

 other "irregular, roundish pores. (The shell is seen in fig. 11 from the apical pole, in fig. lla 

 with the cephalis, in fig. 116 without it, exhibiting the four central collar pores of the cortinar 

 septum.) Mouth truncate, without prominent peristome. 



Dimensions. Cephalis 0'02 long, 0'03 broad ; thorax 01 long, 0'08 broad. 



Habitat. North Pacific, Station 244, depth 2900 fathoms. 



