1030 THE VOYAGE OF H.M.S. CHALLENGER. 



three superior or coryphal spines and three inferior or basal spines ; two of these are odd 

 and dorsal (the apical horn and the caudal foot), the four others are paired and ventral 

 (the frontal horns and the pectoral feet). The numerous species of this genus may be 

 divided into three subgenera, according to the simple or branched shape of the ascending 

 horns and of the descending feet. 



Subgenus 1. Triospyris, Haeckel, 1881, Prodromus, p. 441. 

 Definition. — Horns and feet simple, not branched nor forked. 



1. Triceraspyris tripodiscus, n. sp. 



Shell nut-shaped, tuberculate, with deep sagittal stricture. Pores irregular roundish, two pairs of 

 ■larger pores on each side of the ring. Basal plate with three large pores. Horns and feet slender 

 cylindrical, straight, divergent ; three horns about as long as the shell, three feet twice as long. 



Dimensions. — Shell 0'06 long, 0'08 broad ; horn 0'05 long, feet 01. 



Habitat. — Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms. 



2. Triceraspyris cortiniscus, n. sp. 



Shell subspherical, smooth, with slight sagittal stricture. Pores small and numerous, subregular 

 roundish. Basal plate with two large pores (?). Apical horn conical, short, half as long as the 

 shell and the two lateral horns, which are curved outwards. AU three feet equal, cylindrical, 

 strongly curved and divergent, twice to three times as long as the shell. 



Dimensions. — Shell 0-07 long, 0'08 broad ; horn 0-04 to 0-08 long, feet 015 to 0-2 long. 



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



3. Triceraspyris didiceros, Haeckel. 



Ceratospyris didiceros, Ehienberg, 1875, Abhandl. d. Akad. d. Wise. Berlin, p. 66, Taf. xxi. 

 fig. 6. 



Shell nut-shaped, thorny, with superficial sagittal stricture. Pores large, irregular roundish. 

 Basal plate with four larger pores. Apical horn and caudal foot small, conical, shorter than half 

 the shell. The two frontal horns longer, slender conical. The two pectoral feet very large, 

 cylindrical, nearly parallel, vertical, slightl}' curved, twice to three times as long as the shell. 



Di'mensions. — Shell 0-07 long, 0'09 broad ; two sagittal spines 0"02 long, two lateral horns 

 0-04 long, two lateral feet 015 to 0-25 long. 



Habitat. — Fossil in Barbados. 



Subgenus 2. Triospyrium, Haeckel. 

 Definition. — Horns simple, not branched ; feet forked or branched. 



