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



Dimensions. Main axis of the cortical shell (without tubes) 015, greatest breadth Oil ; pores 

 0-009, bars 0'004 ; length of the polar tubes 0'08, basal breadth 0'04. 



Habitat. Pacific, western tropical part, Station 225, depth 4475 fathoms. 



2. Cannartidium amphicanna, Haeckel. 



"Curious twin Polycystin," Bury, 1862, Polycystins of Barbados, pi. xx. fig. 4. 



Cortical shell thick walled, rough, with regular, circular pores, not broader than the bars ; six 

 to seven on the half meridian, ten to twelve on the half equator of each chamber. Polar tubes 

 cylindrical, at the distal end open (broken off ?), nearly as long as the main axis, about one- third 

 as broad as the equatorial constriction. Both concentric medullary shells spherical. 



Dimensions. Main axis 0'14, greatest breadth O'll ; pores and bars 0'005 ; length of the polar 

 tubes 0-13, breadth of them 0'03. 



Habitat. Fossil in the Barbados deposits. 



3. Cannartidium amphisiphon, Haeckel. 



1 Haliomrna ampliisiplton, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 

 p. 267. 



Cortical shell thick walled, rough, with irregular, roundish pores, twice to five times as broad as 

 the bars ; five to six on the half meridian, nine to ten on the half equator of each chamber. Polar 

 tubes conical, with smaller pores, about as long as one single chamber, half as broad at the base as 

 the equatorial constriction. (This deep-sea form is probably identical with that fossil species 

 which Ehrenberg, in 1844, described as Haliomma amphisiphon, and which he afterwards, in 1875, 

 erroneously identified with his Asfromma entomocora ( = Cypassis entomocora). But the figure given 

 of the latter is quite different from the given diagnosis of the former.) 



Dimensions. Main axis of the cortical shell (without tubes) 013, greatest breadth 0"! ; pores 

 0-006 to 0-12, bars 0'003 ; length of the polar tubes 0'07, basal breadth of them 0'04. 



Habitat. -Tropical Atlantic, Antilles, Station 24, depth 390 fathoms ; fossil in the Tertiary 

 rocks of Bermuda. 



4. Cannartidium bicinctum, n. sp. (PI. 39, fig. 18). 



Cortical shell thick walled, with a thickened ring-shaped protuberance in the greatest breadth 

 of both chambers. Pores subregular, circular, twice to three times as broad as the bars ; seven to 

 eight on the half meridian, thirteen to fifteen on the half equator of each chamber. Polar tubes 

 conical, with smaller pores, somewhat shorter than the greatest breadth, nearly as thick at the base 

 as the outer spheroidal medullary shell (fig. 18). 



Dimensions. Main axis (without tubes) 012, greatest breadth 0'08 ; pores 0'003 to 0-006, 

 bars 0'002 ; length of the polar tubes 0'08, basal thickness 0'03. 



Habitat. South Atlantic, Station 332, depth 2200 fathoms. 



