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



Genus 110. Arachnosphcera, 1 Haeckel, 1862, Monogr. d. Radiol., p. 355. 



Definition. A strosphserida with five to ten or more cortical, concentric, 

 polyhedral, or spherical lattice-shells, composed of a very thin cobweb-like network ; 

 innermost shell with hexagonal (regular) or polygonal (irregular) meshes ; other shells 

 with larger, irregular, polygonal meshes. 



The genus Arachnosphcera (accurately described by me in 1862, loc. cit.) differs 

 from the two preceding genera in the irregular form of the large meshes in all shells 

 (except often the innermost). This is caused by the ramification of the thin threads, 

 which on each shell connect the neighbouring spines. In Arachnopila and Arachno- 

 pegma the threads pass directly and undivided from each spine to the neighbouring 

 spine (three pairs from the three edges), and therefore all the meshes are triangular. In 

 Arachnosphcera they become polygonal by irregular ramification of the threads. There 

 are here no diagonal threads. 



Subgenus 1. Arachnosphcerella, Haeckel. 

 Definition. Pores of the innermost shell regular, hexagonal. 



1. Arachnosphcera oligacantha, Haeckel. 



Arachnosphcera oligacantha, Haeckel, 1862, Monogr. d. Radio!., p. 356, Taf. x. fig. 2, Taf. xi. 

 fig. 3. 



Innermost shell with regular, hexagonal meshes ; its diameter three times as long as the equal 

 distances between every two concentric shells. Fifteen to twenty radial spines scattered at wide 

 intervals, each with six to eight verticils. 



Dimensions. Diameter of the innermost shell 0'12 ; distance between the concentric shells 

 0-04 to 0-05. 



Habited. Mediterranean (Messina), surface, Haeckel. 



2. Arachnosphcera myriacantha, Haeckel. 



Arachnosphcera myriacantha, Haeckel, 1862, Monogr. d. Kadiol., p. 357, Taf. x. fig. 3, Taf. xi. 

 fig. 4. 



Innermost shell with regular, hexagonal meshes ; its diameter twice as long as the equal distance;; 

 between every two concentric shells. At each nodal-point occurs one radial spine with six to eight 

 verticils (spines in all one hundred to one hundred and twenty or more). 



Dimensions. Diameter of the innermost shell 01 ; distance between the concentric shells 

 0-04 to 0-05. 



Habitat. Cosmopolitan ; Mediterranean, Atlantic, Indian, Pacific, surface. 

 1 Arachnosph(rra = Cobweb-sphere ; a;%i/)). ntfalon. 



