REPORT ON THE RADIOLARIA. 835 



2. Dodecaspis trizonia, n. sp. 



Eadial spines thin, cylindrical in the longer inner half, conical in the shorter outer half. The 

 four meshes of each equatorial and each polar plate of equal size, roundish or nearly circular, five to 

 six times as broad as the bars. By-spines straight, denticulated, scarcely half as long as the radius. 



Dimensions. Diameter of the shell 0'12, of the parmal pores 0'012. 



Habitat. South-west Pacific (east coast of New Zealand), Station 169, surface. 



B. Tribe II. Ly eh naspid a, Haeckel, 1881, Prodromus, p. 467. 



Definition. D orataspida with twenty perforated plates or fenestrated shields 

 (each plate at least with four pores), produced by union of the branches of the four 

 crossed apophyses, which arise, opposite in pairs, from each radial spine. The spherical 

 shell is composed of the twenty plates united by sutures (rarely by concrescence). 



Genus 362. Tessaraspis, 1 Haeckel, 1881, Prodromus, p. 468. 



Definition. D orataspida with twenty plates, which are perforated by eighty 

 aspinal pores (four crossed pores in each plate). Surface smooth, without by-spines. 



The genus Tessaraspis introduces the series of Lychnaspida, which comprise all 

 those Dorataspida in which the shell is composed of twenty plates, each of which is 

 perforated by four primary aspinal pores. In Tessaraspis and L/ychnaspis each plate 

 exhibits only these four primary pores, whilst in Icosaspis and Hylaspis they become 

 surrounded by a circle of secondary or coronal pores. If in Stauraspis, the common 

 ancestral form of the Tessaraspida, the four crossed apophyses of each single radial spine 

 became recurved and united together, we should have the typical plate of Tessaraspis, 

 in which the piercing radial spine is surrounded by four crossed pores of equal size. The 

 number of sutural pores, between the neighbouring plates, is variable ; usually each 

 plate is surrounded by a circle of eight to twelve sutural pores. The sutures between 

 the meeting condyles of the apophyses usually remain open ; but in some species they 

 become obliterated (subgenus Tessaraspidium}. 



Subgenus 1. Tessarasparium, Haeckel. 



Definition. Condyles of the neighbouring plates connected by permanent open 

 sutures ; therefore the whole shell is composed of twenty separated pieces of acanthin. 



1 Tessaraspis = Shield with four pores ; 



