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



3. Staurasins furcata, n. sp. 



Eadial spines thin, qnadrangnlar, prismatic ; outer and inner hah'es nearly of equal length. 

 The four apophyses of each spine simply forked (or partly with bifid fork-branches) ; each spine with 

 eight to twelve sutural condyles. Meshes of the shell ten to twenty times as broad as the bars. 



Dimensions. — Diameter of the shell 0-15 ; breadth of the spines and bars O'OOS. 



EahUat. — Central Tacific, Station 266, surface. 



4. Stauraspis stam'acantha, n. sp. (PI. 137, figs. 5, 6). 



Eadial spines thin, in the inner longer half cylindrical, in the outer half conical with 

 thickened base. Four apophyses of each spine doubly forked or dichotomously (more or less 

 irregularly) branched ; each spine with sixteen to twenty-four sutural condyles. Meshes of the 

 shell of very different sizes and forms : the largest ten to fifteen, the smallest two to three, times as 

 broad as the bars. 



Dimensions. — Diameter of the shell 0'14 ; breadth of the spines 0'002 to O'Ol, of the 

 bars 0-002. 



Halntat. — Tropical Atlantic, St<ation 343, surface. 



Geuus 359. Echinaspis,^ Haeckel, 1881, Prodromus, p. 467. 



Definition — D o r a t a s p i d a without perforated plates ; shell composed only of 

 the meeting branches of the four crossed apophyses, w^hich arise (opposite in pairs) 

 from each radial spine. Condyles of the branch-ends bearing by -spines. 



The genus Echinaspis exhibits the same structure of tlie shell as its ancestral 

 form Stauraspis, and differs from it only in the development of by-spines on the 

 sutural condyli. 



1, Echinaspis dichotoma, n. sp. 



Eadial spines cylindrical, thin, outer half longer than the inner. Four apophyses of each 

 spine simply forked (or partly with 1 lifid fork -branches) ; therefore each spine usually possesses 

 eight (sometimes ten to twelve) sutural condyles. Meshes of the shell ten to twelve times 

 as broad as the bars. Each condyle laears a zigzag by-spine, half as long as the radius. 



Dimensions. — Diameter of the shell 012, of the spines 0-004 to 0-006. 



Hahitat. — North Pacific, Station 253, surface. 



1 £f/iinaspis = Urchin with shiehls ;■ ixinoi, uutt!;. 



