634 THE VOYAGE OF H.M.S. CHALLENGES. 



Subgenus 2.. Monozonitis, Haeckel. 

 Definition. Shell with radial spines or thorns, symmetrically disposed. 



3. Monozonium pleurostylum, n. sp. 



Central chamber spherical, smooth, with four to five pores on the half equator. Both wings of 

 the girdle of the same breadth, but somewhat longer than the central chamber, with four to five 

 longitudinal rows of pores. On the poles of the lateral axis two opposite strong conical spines (one 

 in the middle of each wing). 



Dimensions. Diameter of the central chamber - 025 ; breadth of the wings 0'025, length 0'03 ; 

 pores and bars 0'005. 



Habitat. Pacific, central area, Station 265, surface. 



4. Monozonium amphistylum, n. sp. 



Central chamber lentelliptical, one and a half times as long as broad, with three to four pores 

 on the half equator. Breadth and length of each wing somewhat greater than that of the central 

 chamber. .On the latter two strong conical spines, opposite on the poles of the principal or 

 longitudinal axis. 



Dimensions. Length of the central chamber 0'03, breadth 0'02 ; breadth of the wings 0'025, 

 length 0'04 ; pores and bars O004. 



Habitat. South Atlantic, Station 332, surface. 



5. Monozonium staurostylum, n. sp. 



Central chamber lentelliptical, one and a third tunes as long as broad, with four to five pores 

 on the half equator. Both wings of the girdle have the same breadth, but one and a half tunes the 

 length of the central chamber. Four conical radial spines, two opposite on the poles of the lateral, 

 two on the poles of the principal axis. 



Dimensions. Length of the central chamber 0'028, breadth 0'021 ; breadth of the wings O02, 

 length 0-04. 



Habitat. South Pacific, Station 295, surface. 



Genus 280. Dizonium, 1 n. gen. 



Definition. P y 1 o n i d a with simple, spherical or subspherical, central chamber, 

 surrounded by two crossed latticed girdles, one smaller (primary) transverse and one 

 larger (secondary) lateral girdle. 



The genus Dizonium differs from the preceding Monozonium in the possession of 

 two crossed elliptical lattice-girdles. The smaller girdle, immediately surrounding the 



1 Dizonium = WMi two girdles ; hgam'oit. 



