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



6. Amphitholus armatus, u. sp. 



Central chamber twice as broad, but of the same height, as the flat vaulted cupolas. Surface 

 armed with thirty to forty very large three-sided prismatic spines, longer than the major axis of 

 the shell. Pores irregular, roundish, twice to five times as broad as the bars ; eight to nine on the 

 basal semicircle of one cupola. 



Bimcnsions. — Major axis of the shell 0'15, minor axis O'l ; pores 0'006 to 0'015, bars 0'003 ; 

 length of the spines 0-2 to 0-25, breadth 001. 



Habitat. — North Atlantic, Station 353, surface. 



7. Amiihitholus polyacanthus, n. sp. 



Central chamber of the same breadth and height as both cupolas. Surface armed with very 

 numerous (sixty to eigTity) strong conical spines, about as long as the minor axis of the shell. 

 Pores subregular, circular, twice as liroad as the bars ; sixteen to eighteen in the basal semi- 

 circle of one cupola. 



Dimensions. — Major axis of the shell O'lS, minor O'OS ; pores O-QOG, bars 0-003 ; length of the 

 radial spines 0-09, breadth 0006. 



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



8. Amphitholus panicium, n. sp. (PL 10, fig. 4). 



Central chamber ellipsoidal, nearly twice as broad, but of the same height, as both cupolas. 

 "Wliole surface thorny; the largest ladial thorns al)out as long as the medullary shell. Pores 

 irregular, roundish, twice to four times as broad as the bars. On the base of each cupola a cu-cle 

 of ten to twelve larger square pores, separated by radial beams, which are prolonged into stouter 

 free spines. This remarkable formation of the cupolas, very rare in this family, recalls the 

 characteristic formation of the distal chambers of the Panartida and Zygartida ( c.r/., PL 40, 

 figs. 4, 8, &c.), where it is very common. 



Biinensions. — Major axis of the shell 015, minor 01 ; pores O'OOo to 0'012, bars 0'003 ; large 

 square pores 0-02 ; axes of the medullary shell 0'03 and 0-02. 



Habitat. — Indian Ocean, Madagascar, Eabbe, surface. 



Genus 292. Amphitholonium,^ n. geu. 



Definition. — Tholouida with double cortical shell (with external veil), with 

 two hemispherical cupolas, opposite on the poles of one axis ; central chamber (between 

 them) Xc6raacz7^a-shaped, with medullary shell. 



The genus Amphitholonium differs from the nearly allied Amp>hitholiis (probably 

 its ancestral form) only in the duplication of the cortical shell ; the outer has the 



* Amphitholonium = Small shell with two opposite cupolas ; «/«(p(, SoT^avwu. 



