470 DR MURRAY ON THE DEEP AND SHALLOW-WATER MARINE FAUNA 



area both in the South AtLantic and tropical Pacific, while another species {Cenosph(Bm 

 antiqua) occurs both in the tropical and South Atlantic and tropical Pacific. The 

 remainder of tlie species occurring outside this area are each represented in a single 

 region of the ocean, as indicated above. 



LIST Villa. 



The following species of Radiolaria were observed in the surface gatherings taken b}' 

 the Challenger in the Southern Indian Ocean (Station 1.57, lat. 53" 55' S.). Of the 

 24 species enumerated, one-half {i.e., the 12 species of Spumellaria and Nassellaria) were 

 observed also in the bottom-deposit at the same Station, of which 5 species {Stijptosjohxera 

 spongiacea, Cromyomma perspicimm, Rhizosphcera trigonacantha, Porocliscus flustrella, 

 and Cyrtocalpis ovulum) occur also in the tropical Pacific. Of the 12 species of 

 Acantharia and Phseodaria (the skeletons of which apparently pass into solution before, 

 or immediately after, reaching the bottom), 4 species are recorded from other regions, but, 

 curiously enough, only from the Atlantic (while, as stated above, the 5 species of 

 Spumellaria and Nassellaria- occurring outside this area are recorded only from the 

 tropical Pacific), viz., Acanthostaums purpurascens recorded from the surface in the 

 North and tropical Atlantic, Challengeron halfouri recorded from the surface in the 

 North Atlantic, and Dictijocha stapedia and Bistepliamis speculum recorded from the 

 Ijottom in the tropical Atlantic (West Indies, 450 fathoms). 



In striking contrast to the wealth of forms in the deposit at this Station is the 

 uniformity of the Radiolarian surface fauna. This, doubtless, arises from the fact that the 

 tow-nets were only dragged through a relatively small distance of the surface waters, 

 wliereas the deposit at the bottom represents the accumulation of forms which have fallen 

 from the surface during an immense period of time. The absence of some species of 

 Acantharia and Phseodaria in the deposit, when compared with their relative abundance 

 in the surface-net gatherings, is to be accounted for by the structure and composition of 

 the skeletons, which are more readily dissolved after tlie death of the animals. Certain 

 species of Acantharia and Phseodaria are the most abundant on the surface, and these 

 are very rich in individuals. Of the Acantharia the most abundant are Acanthoma 

 claparedei, Acanthosiaurus p)'^^'>purascens, and Amphilonche lanceolata, and of the 

 Phseodaria the species of Chcdlengeron. 



Spumellaeia. 

 a. Sphoeroidea. 



Utijptosjjluera spongiacea, Haeckel. 



AcanthoBphcera antarclica, Haeckel. 



Cromijomma perspicuum, Haeckel. 



Ehimsphiirra trvfmacantha, Haeckel. 

 ,, antarclica, Haeckel. 



h. Diseoidea. 



Porodiscus flustrella, Haeckel. 

 Stijlodictya muUispina, Haeckel. 

 Eucidtonia mudleri, Haeckel. 

 Stylotrochus challervjeri, IlaeckeL 



II. Acantharia. 



Acanthoma clapareild, Haeckel. 

 Acanthostaicrus purpurascens, Haeckel. 



