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



4. Soreuma acervulina, n. sp. 



Shell quite irregular, cloddy, or tuberous, composed of twenty to thirty (or more) roundish 

 chambers of almost uniform size, the largest twice to three times as broad as the smallest. Pores 

 irregular, roundish. Surface smooth. 



Dimensions. Diameter of the shell 0'18 to 0'24, of the largest chambers 0'06, of the smallest 

 0-02. 



Habitat. South Pacific, Station 295, depth 1500 fathoms. 



Subgenus 2. Soreumidium, Haeckel. 

 Definition. Shell with radial spines. 



5. Soreuma spinosum, n. sp. 



Shell quite irregular, cloddy, or tuberous, composed of thirty to forty subspherical chambers of 

 nearly the same size. Pores subregular, circular, twice as broad as the bars ; on the equator of each 

 chamber six to eight pores. Surface thorny, covered with irregularly scattered conical radial 

 spines, about as long as the diameter of the chambers. 



Dimensions. Diameter of the shell 017 to 0'25, of the chambers 0'04. 



Habitat. North Pacific, Station 241, depth 2300 fathoms. 



'6. Soreuma setosum, n. sp. 



Shell nearly spherical, composed of sixty to seventy (or more) irregular, roundish chambers of 

 very different sizes, the largest five to six times as broad as the smallest. Pores irregular, roundish. 

 Surface bristly, covered with very numerous, long and thin, bristle-shaped radial spines, about as 

 long as the diameter of the shell. 



Dimensions. Diameter of the shell 0'28, of the chambers 0'005 to - 03. 



Habitat. Pacific, central area, Station 271, depth 2425 fathoms. 



Genus 316. Sorolarcus, 1 n. gen. 



Definition. S oreumida with numerous chambers, aggregated irregularly around 

 a trizonal medullary shell or Larnacilla -shell. 



The genus Sorolarcus comprises those Soreumida in which the heap of irregularly 

 aggregated chambers encloses a central trizonal medullary shell, by which they demon- 

 strate clearly their descent from Larnacida or Pylonida. The lentelliptical medullary 



1 Sorolarcus = Basket heap ; <ru%o;, Tiajxoj. 



