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



each suture. Both aspinal meshes kiduey-shaped, four times as broad as the small sutural 

 meshes. Eadial spines thick, in the inner longer part cylindrical, in the outer shorter part 

 conical. (Differs from all other species in the mviltiplication of the sutural pores.) 



Dimensions. — Diameter of the shell 0'2, of the aspinal pores 0'016, of the sutural pores 0'004. 



Habitat. — Equatorial Atlantic, Station 347, surface. 



Genus 352. Diporasjiils} n. gen. 



Definition. — Dorataspida with twenty plates, which are perforated by forty 

 aspinal pores (two pores in each plate). Surface of the shell without combs and 

 dimples, l:)ut armed with numerous by-spines. 



The genus Drporaspis has the same characteristic structure of the shell as the 

 typical Dorataspis, and differs from it only in the development of numerous by-spines 

 on the surface. The number of the sutures between the twenty plates is sometimes 

 fifty-two, at other times fifty -four, and in each suture we find occasionally a single pore, 

 at other times two or three such pores. 



Subgenus 1. Dipovaspanum. 



Definition. — Shell with fifty-two sutures, four polar plates on each pole of the 

 main axis meeting in one common j)oint ; therefore all eight polar plates pentagonal 

 and of equal size. Shell therefore composed of four (equatorial) hexagonal plates, and of 

 sixteen pentagonal (eight tropical and eight polar) plates. 



1. Diporaspis nephropora, n. sp. (PI. 134, fig. 15). 



Shell with fifty-two sutures and fifty-two sutural pores, with four hexagonal and sixteen 

 pentagonal plates. Both aspinal pores of each plate kidney-shaped, about twice as broad as the 

 circular sutural pores. Eadial spines thm, cylindrical, longer than the radius. By-spines forked, 

 only one-third as long as the radius. 



Dimensions. — Diameter of the shell 0'13, parmal pores 0'03, sutural pores 0'07. 



Habitat. — North Pacific, Station 244, surface. 



2. Diporaspis circopora, n. sp. 



Shell with fifty-two sutures and one hundred to one hundred and fifty sutural pores, with four 

 hexagonal and sixteen pentagonal plates. Both aspinal pores of each plate circular, very large, six 

 to eight times as broad as the small circular sutural pores (in each suture two to three pores). 



1 Diporaspis = Shield with two jwnes ; SiVofo;, dtiri;. 



