REPORT ON THE RADIOLARIA. 1139 



1. Trissopilium tetraplecta, n. sp. 



Shell in the upper half three-sided pyramidal, in the lower half inversely hemispherical, of 

 equal length and breadth. Pores irregular, roundish, in the upper half larger. From the apex 

 there diverge four equal, straight and stout, three-sided pyramidal spines, one of which is vertically 

 ascending (the horn), the three others obliquely descending (the wings). The distal half of the 

 latter is free, whilst the proximal half forms three ribs, enclosed in the shell-wall. Mouth 

 constricted, half as broad as the shell. 



Dimensions. Shell 0'08 long and broad, horn and wings 01 long. 



Habitat. Central Pacific, Station 268, depth 2900 fathoms. 



2. Trissopilium lithomelissa, n. sp. 



Shell ovate, one and one-third times as long as broad. Pores circular, of different sizes, small 

 and numerous. Apical horn very large, straight, cylindrical, vertical, longer than the shell. Three 

 lateral wings shorter, arising from the middle of the shell, conical, curved, divergent. Mouth 

 truncate, two-thirds as broad as the shell. 



Dimensions. Shell Oil long, 0'08 broad; horn O'l 3 long, wings 0'09 long. 



Habitat. Central Pacific, Station 271, depth 2425 fathoms. 



Genus 500. Archipilium, 1 Haeckel, 1881, Prodromus, p. 427. 



Definition. A rchipilida (vel Monocyrtida triradiata aperta) with three lateral 

 ribs or wings. Mouth truncate, without terminal feet. Apex without horn. 



The genus Archipilium differs from the nearly allied Trissopilium, its probable 

 ancestral form, in the absence of the apical horn. The three lateral wings of the ovate 

 shell are stout spines. It may also be derived from the similar Sethopilium by reduc- 

 tion and loss of the cephalis. 



1. Archipilium orthopterum, n. sp. (PI. 98, fig. 7). 



Shell ovate, smooth, nearly cylindrical, scarcely broader than the truncate, widely open mouth. 

 Pores numerous, irregular, roundish, of very different sizes. Three lateral wings arising from the 

 middle zone, twice as long as the shell, straight, divergent, stout, cylindrical, longitudinally striped. 



Dimensions. Shell 0'08 long, 0'06 broad; wings 015 long. 



Habitat. Central Pacific, Station 272, depth 2600 fathoms. 



2. Archipilium sigmopterum, n. sp. 



Shell ovate, smooth, nearly campanulate, of equal length and breadth, %ne and one-third times 

 as broad as the truncate, slightly constricted mouth. Pores scarce, irregularly formed and 



1 Archipilium= Primordial hat ; 



