REPORT ON THE RADIOLARIA. 619 



The genus Larnacidium has the same shell -formation as the foregoing LarnaciUa, 

 and differs from it only in the possession of radial spines on the surface, which in all 

 known species exhibit a symmetrical disposition. From the nearly allied genus 

 Larcidium it differs in the characteristic mode of connection between the two shells, 

 owing to the different kind of growth. In Larcidium this connection is effected only 

 by radial beams, whereas in Larnacidium (as in all Larnacida) by two lateral 

 latticed tubes, the wings of the primary transverse girdle. 



1. Larnacidium staurobelonimn, u. sp. 



Cortical shell smooth, with four strong, conical, radial spines in the lateral plane, opposite in 

 pairs, two on the poles of the principal and two on the poles of the transverse axis. I'ores sub- 

 regular, circular, twice as broad as the bars ; about twelve on the half meridian. Proportion of 

 the three axes = 2:3:4. Medullary shell spherical, one-third as broad as the cortical shell. 



Dimensions. — Length of the cortical shell 0'12, breadth 0"00, lieight 0-06; pores O'OOS, 

 bars 0-04; medullary shell 0-03. 



Habitat. — North Pacific, Station 244, depth 2900 fathoms. 



2. Larnacidium hexabelonium, n. sp. 



Cortical shell thorny, with six strong, three-sided pyramidal, radial spines, lying opposite 

 in pairs on the poles of the three dimensive axes. Pores siibregular, circular, tlu-ee times as broad 

 as the bars; about fourteen on the half meridian. Proportion of the three axes = 2 : 2-5 :3. 

 Medullary shell spherical, one-third as Ijroad as the cortical shell. 



Dimensions. — Length of the cortical shell 0-14, breadth 0-11, height O'CS; pores 0-01, bars 0-003 ; 

 medullary shell 0-04. 



Habitat. — South Pacific, Station 205, depth 1500 fathoms. 



3. Larnacidium polyhelonimn, n. sp. 



Cortical shell very spiny, with numerous (twenty to thirty or more) larger thin radial spines, 

 about as long as the shell. Pores irregular, twice to five times as broad as the bars; about 

 sixteen on the half meridian. Proixirtion of the three axes =2 : 2-5 : 3. Medullary shell 

 leutelliptical, half as large as the cortical shell. 



Dimensions. — Length of the cortical shell Oil, breadth O'OO, height 0-07; pores 01)04 to 0-0 L 

 bars 0-002 ; length of the medullary .shell 0-06, breadth O'Oo, height 004. 



Habitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms. 



Subfamily 2. Laknacalpida, Haeckel. 



Definition. — L a r n a c i d a with a double, trizonal, Zor?i«ci7/a-shaped medullary shell, 

 enclosed in the central capsule, and enveloped by a simple or double, latticed or spongy, 

 lentelliptical, cortical shell. 



