1286 THE VOYAGE OF H.M.S. CHALLENGER. 



conical, straight wings, of half the length, opposite in pairs in two meridional planes, perpendicular 

 to one another (compare Tetralacorys, PL 65, figs. 4, 5). 



Dimensions. Cephalis 0'03 long, 0'04 broad; thorax 01 long, 0'09 broad. 



Habitat. South Pacific, Station 300, depth 1375 fathoms. 



2. Sethophcena hexaptera, n. sp. (PL 97, fig. 13). 



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

 breadth = 2:4. Cephalis hemispherical, with a conical horn of the same length. Thorax innate, 

 inversely ovate, nearly pear-shaped, with subregular, circular pores. From its upper half arise, by a 

 broad base, six divergent, strong, conical wings, which are horn-like, curved downwards, and half as 

 long as the thorax. 



Dimensions. Cephalis 0'025 long, 0'04 broad ; thorax 0'09 long, 0'08 broad. 



Habitat. Central Pacific, Station 268, depth 2900 fathoms. 



3. Sethophcena enneaptera, n. sp. 



Shell rough, with sharp collar stricture. Length of the two joints = 1 : 6, breadth = 1 : 3. 

 Cephalis subspherical, with a stout conical horn of twice the length. Thorax inversely ovate, with 

 pointed, conical, basal part, and irregular, roundish pores. From its middle part arise, by a broad 

 triangular base, nine compressed, divergent wings, which are a little curved, slender, and about as 

 long as the thorax. 



Dimensions. Cephalis 0'025 long, 0'03 broad ; thorax 017 long, 01 broad. 



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



4. Sethophcena polyptera, n. sp. 



Shell thorny, with slight collar stricture. Length of the two joints = 1 : 10, breadth = 3:8. 

 Cephalis flat, cap-shaped, without horn. Thorax pear-shaped, with hemispherical base and regular, 

 circular pores. From its lower half (beyond the equator) arises a corona of numerous short 

 conical wings (eighteen to twenty-four), which are a little curved, and divergent downwards, scarcely 

 one-third as long as the thorax. 



Dimensions. Cephalis 0'015 long, 0'04 broad ; thorax 015 long, 012 broad. 



Habitat. North Pacific, Station 253, depth 3125 fathoms. 



Genus 571. Clistophcena, Haeckel, 1881, Prodromus, p. 433. 



Definition. S ethophsenida (vel Dicyrtida multiradiata clausa) with terminal 

 apophyses. Cephalis with a horn. 



1 Clistophcena = Closed shell ; <fi)(u, (p tiiva,. 



