810 THE VOYAGE OF H.M.S. CHALLENGES. 



condyles, very thiu, pointed. In the specimens of this remarkable species, which I first observed in 

 Messina, two opposite equatorial spines had quite free apophyses, not connected with the neighbour- 

 ing spines ; therefore the thin lattice-work of the shell exhibited only thirty-six sutures and twenty 

 meshes (two meshes with six sutures, six meshes with four sutures, and twelve meshes with three 

 sutures). In similar specimens, which I afterwards observed in the Canary Islands, all four 

 equatorial spines were connected in the same manner with the neighbouring spines ; therefore they 

 possessed forty sutures and twenty-two meshes, like Phractaspis prototypes (PI. 137, fig. 2). 

 Perhaps the Mediterranean species represents a peculiar genus, Phractasplenium Upenne. 



Dimensions. Di&m&t&T of the shell 01, of the meshes O03 to 0'05 ; breadth of the spines 

 0-002. 



Habitat. Mediterranean (Messina), Canary Islands (Lanzerote), surface. 



Subgenus 2. Phractaspidium, Haeckel. 



Definition. Shell with forty to eighty or more meshes, and eighty to one 

 hundred or more sutures. Each spine with six to eight or more branches, its two 

 apophyses being doubly forked or more ramified. 



5. Phractaspis constricta, n. sp. (PL 137, fig. 3). 



Eadial spines strongly compressed, two-edged, pointed ; their outer half twice constricted and 

 somewhat longer than the inner half. Each spine with two opposite forked apophyses, the branches 

 of which are again forked ; therefore eight condyles on each spine. The network of the spherical 

 shell with eighty sutures and sixty-two meshes (twenty-two large primary meshes and forty smaller 

 secondary meshes, the latter between the distal fork-branches). 



Dimensions. Diameter of the shell Oil, of the large meshes 0'04 to 0'05, of the small 

 meshes O'Ol ; breadth of the spines O'Ol. 



Habitat. South Atlantic, Station 348, depth 2450 fathoms. 



6. Phractaspis cataphracta, Haeckel. 



Acanthometra cataplimcta, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 49, 



Taf. x. figs. 7, 8. 

 Dorataspis eatapltracia, Haeckel, 1862, Monogr. d. EadioL, p. 415. 



Eadial spines thin, quadrangular ; their outer pyramidal part shorter than the inner. Each 

 spine with six to eight condyles, the fork-branches of their two opposite apophyses being (all or 

 partly) again forked. The network with sixty to eighty sutures and meshes : sometimes as regular 

 as in the preceding species, at other times more or less irregular. 



Dimensions. Diameter of the shell 01, of the meshes 0'02 to 0'04 ; breadth of the bars 0'004 

 to 0-008. 



IToUtat. Mediterranean (Cette), Miiller (Messina), Haeckel ; North Atlantic, Station 353, surface. 



