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



here we cannot certainly say whether the former have originated from the latter by reduc- 

 tion of the Larnacilla-shdl, or whether both groups be of different origin. The latter is 

 perhaps more probable. This family as well as the foregoing requires a much more careful 

 study than I could give to it. 



Synopsis of the Genera of Streblonida. 



I. Subfamily 1 ghell without ra( j ia i sp j nes . 310. Streblonia. 



Streblacanthida. I 



Primordial chamber simple, spherical or f shell with rajial ines> Sll. Streblacantha. 



lentelliptical. 



II. Subfamily 



Streblopylida. , ghell without radia i sp i nes . .312. Streblopyle. 



Primordial chamber trizonal or Larnacilla- 

 shaped. 



Genus 310. Streblonia, 1 n. gen. 



Definition. Streblonida with simple, spherical, subspherical, or lentelliptical 

 primordial chamber, beginning the screw-like series of spirally ascending chambers. 

 Surface smooth or thorny, without radial spines. 



The genus Streblonia contains those Streblonida in which a variable number of 

 roundish, subspherical, or longish chambers form a screw-like aggregate, beginning with 

 a quite simple primordial chamber. The special order of the complex spiral offers in- 

 teresting resemblances to different genera of the calcareous Foraminifera, from which I 

 have taken the corresponding names of the species. The whole form of the shell is 

 sometimes more egg-shaped or subspherical, at other times more top-like or conical, 

 occasionally very flat. Its surface is smooth or rough, but not covered with radial spines. 



1. Streblonia globigerina, n. sp. 



Shell subspherical, thick walled, clustered, with eight to ten nearly spherical chambers, of rapidly 

 increasing size, the tenth chamber about twelve times as broad as the first. Breadth of the shell 

 nearly -equal to the height. Pores subregular, circular, hexagonally framed, of about the same 

 breadth as the bars; about sixteen on the breadth of the tenth chamber. (Resembles very much the 

 common Globigerina.) 



Dimensions. Breadth of the shell 0'18, height 0'16. 



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



2. Streblonia uvigerina, n. sp. 



Shell nearly egg-shaped, clustered, with eight to eleven subspherical chambers of gradually 

 increasing size, the tenth chamber about six times as broad as the first. Breadth of the shell about 



1 Streblonia,-- Screw-shell ; rrpf&inni. 



