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



2. Pityomma piniferum, n. sp. 



Cortical shell thiu walled, with irregular, roundish pores, connected with hoth medullary 

 shells by twenty stout radial beams, which are prolonged outside into twenty large three-sided 

 prismatic spines. These are longer than the shell diameter, and have three dentate edges, being 

 branched like a pine tree (with four to six ramified branches on each edge, decreasing in 

 size towards the distal end) ; similar to those of C'ladococcus ahictimis (PI. 27, fig. 3). Eadial pro- 

 portion of the three spheres = 1:2:8. Both medullary shells with regular, circular pores, twice 

 as broad as the bars. 



Dimensions. — Diameter of the outer shell 0'2, middle Ovi, inner 0-25 ; length of the 

 spines 0'25. 



Habitat. — South Pacific, Station 299 (Juan Fernandez), surface. 



3. Pityomma dryriiodes, n. sp. (PI. 29, fig. 9). 



Cortical shell thin walled, connected with both medullary shells by very numerous (one hundred 

 to two hundred or more) very thin radial beams, which are prolonged outside into thin branched 

 radial spines, scarcely half as long as the shell radius, each spine bearing six to nme simple 

 branches. Outer and middle shell uneven, with hiU-shaped protuberances and valleys between 

 them ; the connecting radial beams, which arise fi-om the top of the protuberances of the middle 

 shell, are inserted into the deepest part of the valleys of the outer shell. Eadial proportion of 

 the three spheres = 1:3:8. Outer medullary shell with small, irregular, roundish, or polygonal 

 pores, not much broader than the bars ; innermost shell witli polygonal pores and very thin bars. 



Dimensions. — Diameter of the outer .shell 0-28, middle 0-01, inner 0-033 ; length of the spines 

 0-07, breadth 0-004. 



Hahitett. — Central Pacific, Station 271, surface. 



Subfamily Cromyommida,^ Haeckel, 1881, Prodromus, jap. 449, 453. 

 Dcjinition. — A s t r o s p h ae r i d a witli four concentric spherical lattice -shells. 



Genus 104. Cromyomma'^ Haeckel, 1881, Prodromus, p. 454. 



Definition. — A s t r o s p h as r i d a with four concentric lattice-spheres and numerous 

 simple radial spines of one kind. 



The genus Cromyomma is the common ancestral form of the Cromyommida, or 

 of those Astrosphasrida in wliich the shell is composed of four concentric spheres, 

 connected by radial beams. Usually two of these are intracapsular or medullary 



1 Cromyommida = Astrospli8eriJa qiiadniplicia = Tetraspliaeria polyacantha. 



2 Cromijommn = Onion-eye ; x(^6uuoy, o,ufcv. 



