REPOET ON THE RADIOLARIA. 1265 



third are separated by the same luunher of large, triangular meshes, in the middle third connected 

 by irregular network, in the distal third free. 



Dimensions. — Cephalis 0-02 long, 0-03 broad ; thorax 0-06 long, CIS broad. 



Habitat. — Central Pacific, Station 273, depth 2350 fathoms. 



Genus 564. Arachnocorys,^ Haeckel, 1860, Monatsber. d. k. preuss. 

 Akad. d. Wiss. Berlin, p. 837. 



Definition. — S e t li o p h o r m i d a (vel Dicyrtida multiradiata aperta) with numerous 

 radial ribs hi the wall of the pyramidal thorax, prolonged into divergent terminal feet. 

 Network double, with an arachnoidal outer mantle around the inner lattice -shell. 

 Cephalis commonly with numerous horns. 



The genus Arachnocorys has been derived from the preceding Acanthocorys, by 

 development of numerous external siliceous threads which connect the radial horns of 

 the cephalis -udth the secondary spines arising from the thoracic ribs. In this way 

 there becomes formed an outer arachnoidal framework, enveloping loosely, like a delicate 

 mantle, the inner primary lattice-shell. 



Subgenus 1. Arachnocorallium, Haeckel. 



Definition. — Thorax with six divergent ribs or radial beams (three primary or 

 perradial, alternating with three secondary or interradial). 



1. Arachnocorys hexai^tera, n. sp. 



Arachnocorys circumtexta (juv. ]), R. Hertwig, 1879, Organism, d. Radiol, p. 79, Taf. viii. 

 fig. 2a. 



Cephalis large, subspherical, with irregular, polygonal pores, and numerous bristle-shaped spines 

 twice the length ; on the centre of the top a single larger vertical horn. Thorax flatly conical, with 

 six strong and straight widely divergent ribs, which in the proximal half are separated by six large 

 holes, in the distal half connected by a broad ring of irregular network. From each rib arises a 

 perpendicular branch, and these branches are connected together, and with the spines of the cephalis, 

 by arachnoidal network. 



Dimensions. — Cephalis 0'04 diameter, thorax O^OS long, 0'24 broad. 



Habitat. — Central Pacific, Station 266 ; Mediterranean, surface. 



2. Arachnocorys discoides, n. sp. 



Cephalis small, pyramidal, with irregular, roundish pores and numerous thin spines, on the top 

 a single larger vertical horn. Thorax very flat, nearly discoidal, with six strong and straight ribs, 



1 Arachnocorys - helmet with a cobweb ; ifax^ii "-''^"s- 

 (ZOOL. CHALL. EXP. PART XL. — 1886.) Kr 159 



