REPORT ON THE RADIOLARIA. 1603 



d. Radiol., p. 91, Taf. ix. fig. 4). He too observed only fragments of destroyed 

 and incomplete shells, and was led by their striking similarity to fragments of 

 AulospJuera elegantissima to unite it with the genus Aulosphosra. But the accurate 

 description and the figure given by him of the fragments observed leaves no doubt 

 that it was a true Sagoscena. 



In the collection of the Challenger the Sagosphserida are so common and so richly 

 represented, that we may describe here not less than seven genera and thirty-three 

 species, but this may be a small part only of the numerous species of this family, which 

 seems to be widely distributed over all oceans, in the Arctic and Antarctic as well 

 as in temperate and tropical zones. The majority are inhabitants of the surface, but a 

 few species have been found only in deep-sea soundings. A striking fact is their usual 

 association with the similar Aulosphsericla. The majority of shells of both families 

 were found entangled in one another. 



The shell of all Sagosphserida seems to be spherical or nearly spherical in the complete 

 state ; but complete spheres can be observed only very rarely, and it is not impossible 

 that deviations from the spherical form exist just as in some Aulosphserida (e.g., the 

 lenticular Aulophacus and the spindle-shaped Aulatractus). The diameter of the 

 spheres usually seems to be between 1 and 2, often also 3 millimetres ; very rarely 

 shells occur which are less than 1 or more than 3 (4 or 5) millimetres. 



The siliceous network or lattice-work of the Sagosphserida exhibits a very character- 

 istic shape, and this enables one to distinguish it at first sight from all the other Radiolaria, 

 It is constantly composed of triangular, very large meshes, which are separated by very 

 thin and delicate, flexible and elastic bars. With respect to the arrangement of these 

 meshes we distinguish two different subfamilies ; in the Sagenida the wall of the spherical 

 shell is very thin and composed only of a simple lattice-plate ; in the Sagmarida the 

 wall is thickened and spongy, with a complete wicker-work of threads, interwoven in 

 different directions. 



The typical triangular form of the large meshes is usually regular or subregular in 

 the fenestrated Sagenida, more or less irregular in the spongy Sagmarida. In many 

 cases, however, irregular triangles also occur in the former, and regular triangles in the 

 latter subfamily. Very rarely irregular polygonal meshes are found in a part of the 

 network, small connecting bars being developed accidentally between two neighbouring 

 sides of the triangles. The diameter of the meshes is usually between O'l and 0'2 mm., 

 often also greater, between 0'2 and 0'3, rarely smaller, 0'05 to 0"09 mm. The triangular 

 meshes of the Sagosphaerida are therefore on an average ten times as large as the usual 

 meshes in the network of the common Sphseroidea. 



The filiform bars, or the thread-shaped, very long and thin rods between the 

 triangular meshes, are scarcely less characteristic of the Sagosphserida than the form and 

 size of the meshes. Their length is usually between O'l and 0'2 mm., often also 



