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



2. Cai'yomma irregulare, n. sp. 



Eadial proportion of the six shells = 1:2-5:8: lO'o : 13 : 15). Both inner (medullary) shells with 

 regular, circular pores, the other four (cortical) shells with irregular, roundish pores, gradually 

 increasing in size from the innermost to the outermost shell. Eadial spines sixty to eighty, 

 pyramidal, irregularly disposed. 



Dimensions. — Diameter of the six shells — (A) 0-3, (B) 0-26, (C) 0-21, (D) 016, (E) 0-05, (F) 0-02. 



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



Genus 108. Arachnopila,^ n. gen. 



Definition. — A s t r o 8 p h as r i d a with five to ten or naore cortical, concentric, 

 jjolyhedral, or spherical lattice -shells, comjaosed of a very thin coliweb-like network ; 

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

 with simple triangular meshes, without diagonal threads between them. 



The genus Arachnopila, together with the two following genera, forms the peculiar 

 small group of large Arachnosphserida, separated from the true Caryommida by the totally 

 different structure and disposition of the numerous concentric shells ; the former exhibits 

 a similar relation to the latter that the Diplosphserida bears to the Elatommida among 

 the dispherical Haliommida. The concentric shells (five to ten or more) lie outside the 

 central capsule, and are composed of very delicate, cobweb -like threads. From the 

 innermost shell arise numerous, three-sided prismatic, very long spines, from which at 

 equal regular distances arise lateral branches (three pairs from each sjaine, and one pair 

 from each corner). In Arachnopila these threads pass directly from one spine to the 

 other, and form simple, large, triangular meshes between them. The concentric shells 

 are not connected by interwoven diagonal threads. 



1. Arachnopila hexagonella, n. sp. 



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

 hetween every two concentric shells. Eadial spines twenty to forty, each with twenty to twenty- 

 four verticils. 



Dimensions. — Diameter of the innermost shell O'l ; distance between the concentric shells 0-05. 



Habitat. — Central Pacific, Station 271, surface. 



2. Arachnopila polygonella, n. sp. 



Innermost shell with irregular, polygonal pores ; its diameter fully as long as the equal 

 distance between every two concentric shells. Eadial .spines sixty to eighty, each with twelve to 

 sixteen verticils. 



Dimensions. — Diameter of the innermost shell 0'04 ; distance between the concentric shells 0'04. 



Hahitat. — Central Pacific, Station 266, surface. 



' .4 !-«c/iKopi7« = Cobweb ball ; a^ixun. iny^o;. 



