REPORT ON THE RADIOLARIA. 453 



(commonly between ten and twenty) is also here variable in one and the same 

 species. The greater number of observed species of Astrophacus resemble in a very 

 remarkable manner the corresponding species of Heliodiscus, and differ only in the 

 double medullary shell. 



Subgenus 1. Astrophacetta, Haeckel. 



Definition. Surface of the disk smooth, without radial spines. Bases of the 

 marginal spines free, without a connecting equatorial girdle. 



1. Astrophacua asteriscus, n. sp. 



Disk with smooth surface, three times as broad as the outer and eight times as broad as the inner 

 medullary shell. Pores regular, circular ; twelve to fourteen on the radius. Marginal spines 

 fifteen to twenty, of variable size and disposition ; the largest as long as the radius of the disk, as 

 broad at the base as one pore. (Very similar to Hdiodiscus asteriscus, PI. 33, fig. 8, but differing 

 in the double medullary shell.) 



Dimensions. Diameter of the disk - 2, of the outer medullary shell 0'07, of the inner - 025 ; 

 length of the marginal spines - 05 to 01, basal breadth O'Ol. 



Habitat. Central Pacific, Station 265, depth 2900 fathoms. 



2. Astrophacus trochiscus, n. sp. (PI. 34, fig. 14). 



Disk with smooth surface, three times as broad as the outer and seven times as broad as the 

 inner medullary shell. Pores irregular, roundish ; twelve to thirteen on the radius. Marginal spines 

 sixteen to twenty, conical, of irregular variable size and disposition ; the largest as long as the 

 inner medullary shell. (Differs from Hdiodiscus trockiscus in the double medullary shell.) 



Diinensions. Diameter of the disk 0'22, of the outer medullary shell - 08, of the inner 0'03. 



Habitat. North Atlantic, Station 354, surface. 



3. Astrophacus Solaris, n. sp. (PI. 32, fig. l). 



Disk with smooth surface, three times as broad as the outer and seven times as broad as 

 the inner medullary shell. Pores subregular, roundish ; twelve to fourteen on the radius. 

 Marginal spines one hundred to one hundred and twenty, conical, flexuose, of irregular size and 

 form ; the largest one-third as long as the diameter of the disk. The spines lie not only in the 

 equatorial plane (as is usual) but also in two to four crowded girdles on both sides of it. (Very 

 similar to Heliodiscus solastcr, PL 34, fig. 4, but of double the size, with double the number of 

 spines and with a double medullary shell) 



Dimensions. Diameter of the disk 0'3, of the outer medullary shell Oil, of the inner 0'045; 

 length of the spines 0'03 to 01, basal breadth O'Ol to 0'02. 



Habitat. Indian Ocean, Sunda Strait, Eabbe, surface. 



