S56 THE VOYAGE OF H.M.S. CHALLENGER. 



2. Octopelta furceUa , n. s]^. 



Apophyses of the eight tropical spines forked, each with two parallel simple fork-branches, 

 about as long as their distance from the outer shell. On the base of each spine (in the outer shell) 

 two kidney-shaped aspinal pores, about twice as broad as the other irregular pores. 



Dimensions. — Diameter of tlie outer shell O'l, of the inner 0-04. 



Habitat. — South Atlantic (off Tristan d'Acunha), Station 332, surface. 



3. Octopelta scutella, n. sp. (PI. 133, fig. 5). 



Apophyses of the eight tropical spines crossed by a transverse beam, which is again crossed by 

 two perpendicular branches ; by union of these branches each tropical spine forms a square shield 

 with four crossed pores and twelve to sixteen marginal spikes. On the base of each spine (in the 

 surface of the outer shell) four crossed aspinal pores which correspond to those of the free shields ; 

 these are somewhat larger than the other pores. 



Dimensions. — Diameter of the outer shell 0-12, of the inner ODG. 



Hahitat. — Tropical Atlantic, Station 348, surface. 



Genus 369. Dorypelta} Haeckel, Prodroinus, p. 369. 



Dejinition. — P li ra c t op e 1 1 i da with eight simple spines (four equatorial and 

 four hydrotomical polar spines) and with twelve spines protected by external free 

 apophyses (eight tropical and four geotomical polar spines). 



The genus Donjpelta, the most common of all Phractopeltida which are protected by 

 free apophyses, exhibits a very peculiar differentiation of its twenty radial spines. There 

 are constantly eight simjale spines and twelve spines with apophyses. The eight simple 

 spinBS are the four equatorial spines and four polar spines placed in the hydrotomical 

 median plane. The four other polar spines (placed in the geotomical meridian plane) 

 and the eight tropical spines are protected hj two opposite apophyses, which are now 

 simple, now branched or shield-shaped. A similar difi'erentiation occurs in no other 

 Acanthophractida. 



Subgenus 1. Dorypeltarium, Haeckel. 

 Definition. — Free apophyses of the radial spines simple, not branched. 



' />or!/yei(o= Spear with a light shield ; Soju, s-sXtji. 



