1136 THE VOYAGE OF H.M.S. CHALLENGED. 



feet, and connected in the apex of the pyramidal or campanulate shell with the apical 

 horn. It may probably be derived from Dictyophimus by loss of the ceplialis. The 

 central capsule is simple, spherical, or ellipsoidal. 



1. Tripocalpis plectaniscus, n. sp. 



Shell three-sided pyramidal, smooth, about as long as broad, with irregular polygonal pores and 

 thin bars. Apical horn stout, three-sided pyramidal, about as long as the shell. From the three 

 edges of its base arise three prominent straight radial ribs, which are prolonged into three large 

 divergent feet, of equal size and the same form as the horn. 



Dimensions. Shell 01 diameter, horn and feet 012. 



Habitat. Tropical Pacific (Philippine Sea), Station 206, depth 2100 fathoms. 



2. Tripocalpis galea, Haeckel. 



Halicalyptra galea, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. ii. fig. 10. 



Shell campanulate, rough, about as long as broad, with irregular roundish pores and thick bars. 

 Apical horn stout, three-sided pyramidal, scarcely one-fourth as long as the shell. Beyond its 

 base there arise three prominent, slightly curved lateral ribs, which are prolonged into three pyramidal, 

 slightly divergent stout feet, somewhat shorter than the shell 



Dimensions. Shell 0'08 to 0'09 diameter, horn 0'02, feet 0'07. 



Habitat. Fossil in Barbados. 



3. Tripocalpis tricostata, n. sp. 



Shell ovate campanulate, one and a half times as long as broad, with regular circular pores, 

 disposed in alternate longitudinal rows. Apical horn three-sided pyramidal, stout, half as long as 

 the shell. In the middle of the shell there arise three wing-like lateral ribs, which are prolonged 

 into three broad, slightly curved, divergent terminal feet. 



Dimensions. Shell 012 long, 0'08 broad, horn and feet O'OG to 0'08. 



Habitat. Fossil in Barbados. 



4. Tripocalpis triserrata, n. sp. (PI. 51, fig. 6). 



Shell ovate, nearly twice as long as broad. The three sides of the shell, between the three 

 large ribs, are provided each with nine delicate parallel, longitudinal, slightly curved ribs, alternating 

 with ten longitudinal rows of regular circular pores about as broad as the bars. Apical horn short 

 and broad, three-sided pyramidal ; from the three edges of its base there arise three wing-like serrate 

 main ribs, which are prolonged into three short pyramidal terminal feet. 



Dimensions. Shell 012 long, 0'07 broad, horn and feet O'Ol. 



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



