REPORT ON THE RADIOLARIA. 151 



Family VIII. STAUROSPH^ERIDA, Haeckel (PI. 15). 



Stauroyphcenda, Haeckel, 1881, Prodromus, p. 449. 



Definition. S phseroidea with four radial spines on the surface of the spherical 

 shell, forming a regular cross, being opposite in pairs ""in two axes perpendicular to one 

 another ; living solitary (not associated in colonies). 



The family Staurosphserida is distinguished from the other Sphaeroidea 

 by the possession of four radial spines, which are opposite in pairs in two perpendi- 

 cularly crossed axes. By these " two main axes " an equatorial plane is determined, 

 which approximates them to the D i s c o i d e a. But in the latter the shells as well 

 as the central capsule become more or less flattened, lenticular, or discoidal, whilst 

 in the former they remain spherical. However, some forms of both groups are very 

 similar, and inspection from different sides (and mainly from the margin of the 

 equatorial plane) is required to- determine certainly the spherical (not compressed) shell- 

 form of the Staurosphasrida. As a rule the species of this family are much rarer, and 

 much less numerous, than those of all other Sphseroidea. 



The most simple Staurosphserida are the Staurostylida, with one single spherical 

 lattice-shell. To this ancestral group all other subfamilies can be opposed as 

 " Staurosphasrida concentrica," since their carapace is composed of two or more concentric 

 lattice-shells ; two in the Staurolonchida, three in the Stauracontida, four in the 

 Staurocromyida, five or more in the Staurocaryida. In all these four subfamilies 

 the concentric shells are simple (not spongy) fenestrated spheres. In a sixth sub- 

 family, in the Staurodorida, the shell is wholly or partially composed of irregular 

 spongy wickerwork, with or without a medullary shell in the centre. 



TJie Four Radial Spines in all Staurosphaerida are normally opposed in pairs in 

 two axes perpendicular one to another, and therefore together form a rectangular cross. 

 But in many species besides this normal form individual abnormalities occur, in which 

 the four spines in the equatorial plane are not quite accurately opposed, so that the four 

 angles between them are not right angles, but more or less unequal. More rarely also 

 their position in the equatorial plane is not accurately retained, so that they are placed in 

 two, three, or four different meridian planes, intersecting at very small variable angles. 



In the greater part of Staurosphserida all four radial spines are quite equal, and of the 

 same size and form. But in some genera there takes place a more or less considerable 

 differentiation of the four spines, commonly in pairs, so that the two opposite spines of 

 each pair are equal, but the pairs different (Staurostylus, Staurolonchidiutn). More 

 rarely also both spines of one pair become unequal, whilst those of the other pair remain 

 equal (Stauroxiphos). Very rarely all four spines assume a different size or form. 



