1564 THE VOYAGE OF H.M.S. CHALLENGER. 



from this by eight short teeth, four centripetal on the larger lower ring and four perradial centri- 

 fugal on the smaller upper ring. 



Dimensions. Diameter of the basal ring 0'03, of the apical ring 0'015. 



Habitat. Fossil in Tertiary rocks of Sicily, Caltanisetta (Ehrenberg) ; living in the Central 

 Pacific, Station 270 to 272, surface. 



3. Distephanus staur acanthus, Haeckel. 



Dictyocha stauracantlius, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 76 ; 

 MikrogeoL, 1854, Taf. xxxiil, Ni. xv. fig. 10. 



Each pileated piece of the skeleton exhibits four lateral meshes around the central mesh, and is 

 composed of two horizontal rings, which are connected by four perradial beams arising from the 

 corners of the upper and smaller square ring. Lower ring octagonal, with eight peripheral adradial 

 spines, and with four interradial centripetal teeth on the inside. 



Dimensions. Diameter of the basal ring 0'02, of the apical ring 0'004. 



Habitat. Fossil in Tertiary rocks of North America (Hollis Cliff, Virginia ; Norwich, 

 Connecticut). 



4. Distephanus asteroides, n. sp. 



Dictyocha asteroides, Haeckel, 1881, Prodromus. 



Each pileated piece of the skeleton exhibits five lateral meshes around the central mesh (or the 

 upper ring). Five peripheral spines (on the corners of the lower ring) simple, not articulated. 

 Dimensions. Diameter of the basal ring 0'02, of the apical ring, 0'007. 

 Habitat. Central Pacific, Station 272, depth 2600 fathoms. 



5. Distephanus pentasterias, Haeckel. 



Dictyocha pentasterias, Ehrenberg, 1839, MikrogeoL, Taf. xviii. fig. 61. 



1 Dictyocha quinaria, Ehrenberg, 1842, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 265. 

 1 Dictyocha elegans, Ehrenberg, 1844, Monatsber. d, k. preuss. Akad. d. Wiss. Berlin, p. 80 ; 

 MikrogeoL, 1854, Taf. xxii. fig. 51. 



Actiniscus elegans, Ehrenberg, 1854, MikrogeoL, Taf. xxii. fig. 51. 



Each pileated piece of the skeleton exhibits five lateral meshes around the central mesh (or the 

 upper ring). Five peripheral spines (on the corners of the lower ring) articulated, triangular, with 

 three distinct joints (tapering towards the distal end). 



Dimensions. Diameter of the basal ring 0'012 to - 018, of the apical ring 0'002 to O'OOS. 



Habitat. Cosmopolitan ; living in the depths of the Atlantic and Central Pacific, Stations 247, 

 270 to 272, depths 2530 and 2600 to 2925 fathoms ; fossil in Tertiary deposits (Tripel of Cal- 

 tanisetta, Sicily ; Richmond, Virginia). 



