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



Subfamily Haliommida/ Haeckel. 

 DiplosphcBrida, Haeckel, 1881, Prodromus, pp. 449, 451. 



Definition. — A s t r o s p h ae r i d a with two concentric spherical lattice-shells, 

 united by radial beams. 



Genus 94. Haliomma,^ Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 128. 



Definition. — As t r osphseri d a with one medullary (intracapsular) and one 

 cortical (extracapsular) shell, which are connected by radial beams, piercing the central 

 capsule. Shell surface covered with simple radial spines of the same kind. 



The genus Hcdiomma, one of the oldest known Eadiolarian genera, contained in the 

 catalogue of its discoverer, Ehrenberg, a large number of very different Sphser ell aria, 

 belonging to at least sixteen different genera. We limit here the conception of 

 the genus to those Haliommida which bear simple radial spines of one kind on the 

 surface of the cortical shell (the latter being separated from the medullary shell liy the 

 central capsule). 



Subgenus 1. Haliommantha, Haeckel. 



Definition. — Pores of the cortical shell regular, of nearly equal size and similar 

 form; spines on the whole surface (commonly one spine at each nodal -point). 



1. Haliomma hexagonium, n. sp. 



Cortical shell four times as broad as the medullary shell, both having very thiu thread-like bars, 

 and reoailar, hexagonal pores (eighteen to twenty on the radius of the outer, five to six on the radius 

 of the inner shell). The two shells connected by twenty thin thread-like radial beams. At each 

 nodal-point of the outer shell arises a bristle-shaped radial spine, half as long as the radius. 

 (Similar to Heliosoma radians, PI. 28, fig. 3, but with aU the spines equal.) 



Dimensions. — Diameter of the outer shell 0-2, inner 0-05 ; pores of the outer 0-015, of the inner 

 O-Ql ; length of the spines O'OS. 



Habitat. — Equatorial Atlantic, Station 347, surface. 



2. Haliomma arachnium, n. sp. 



Cortical shell three times as broad as the medullary shell ; pores of the former regular, hexa- 

 gonal, with very thin thread-like bars (fourteen to sixteen on the radius) ; pores of the latter regular, 



1 Haliommida = Astrosphaerida duplicia = Dyospha?rida polyaoantha. 

 - HaliomiiM = Sea.-eje ; ctT^S: o/ifta. 



