1632 THE VOYAGE OF H.M.S. CHALLENGER. 



Dimensions. Horizontal diameter of the lens 6'0, vertical main axis T2 ; length of the radial 

 tubes 0-2, breadth 0'005. 



Habitat. Indian Ocean, Madagascar (Eabbe), surface. 



Genus 687. Aulatractus, 1 n. gen. 



Definition. Aulos ph serid a with triangular meshes in the network, the 

 tangential tubes of which form an ellipsoidal or spindle-shaped, simple lattice-shell, with 

 prolonged vertical main axis. Radial tubes arise at its nodal points. 



The genus Aulatractus differs from all the other Aulosphaerida in the peculiar 

 prolongation of the vertical axis of the lattice-sphere, by which the latter becomes 

 ellipsoidal or spindle-shaped. The triangular meshes of the regular lattice-work become 

 usually more or less irregular and polygonal at the two poles of the elongated main 

 axis. Aulatractus seems to be developed from Aulosphcera in the opposite way from 

 Aulophacus, the former by elongating, the latter by shortening of the vertical main-axis. 



1. Aulatractus fusiformis, n. sp. (PI. Ill, figs. 6, 6a, 6b). 



Shell spindle-shaped, about twice as long as broad, rounded at both poles of the main axis. 

 Tangential tubes smooth, cylindrical. Eadial tubes of the same length as the tangential tubes, but 

 much thinner, slender cylindrical, studded with perpendicularly arising, short, lateral branches, which 

 are scattered in the proximal part, verticillate in the distal part, and bear a spinulate terminal knob. 



Dimensions. Length of the shell 7'5 to 10 - 0, breadth 3'5; length of the radial tubes 015 to 018, 

 breadth O004. 



Habitat. Tropical Atlantic, Stations 348, 349 ; surface, and in various depths. 



2. Aulatractus diploconus, n. sp. (PI. Ill, fig. 7). 



Shell diploconical or nearly spindle-shaped, about three times as long as broad, equally pointed 

 at the two poles of the main axis, not inflated in the middle part. Eadial tubes slenderly conical, 

 thorny, only half as long as the smooth tangential tubes. 



Dimensions. Length of the shell 6'0 to 8'0, breadth 2'2 to 4'5 ; length of the radial tubes 01 

 to 015, breadth 0'007. 



Habitat. North Atlantic, Canary Islands, Station 353, surface. 



3. Aulatractus fusulus, n. sp. 



Shell spindle-shaped, about twice as long as broad, pointed at the two equal poles of the main 

 axis. Eadial tubes cylindro-conical, smooth, about as long as the smooth tangential tubes. This 



1 A ulatractus = Spindle composed of tubes; aiAo'f, ZTJ*TO;. 



