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



Subgenus 4. Hexalonchusa, Haeckel. 



Definition. — Pores of the cortical shell in-egular, of different size or form ; surface 

 covered with numerous conical or bristle-shaped, radial by-spines. 



22. Hexalonche philosophica, n. sp. (PI. 22, fig. 4). 



Cortical shell thin walled, covered with short conical spines, three times as broad as the 

 medullary sheU. Pores irregular polygonal, or more roundish, twice to six times as broad as the 

 bars ; six to eight on the radius. Inner shell of the same structure, pores three times smaller, 

 connected with the outer by six very thin radial beams, which are prolonged outside into six strong, 

 triangular pyramidal spines, as long as the radius. (Similar to Hexalonche anaximandri, PI. 22, fig. 5, 

 but different in the irregular network and the shorter by-spines.) 



Dimensions. — Diameter of the outer .shell 0"11, pores 0'005 to O'OI.d, bars 0"0025 ; inner shell 

 0-04 ; length of the spines 0-06, breadth 0-02. 



Hahitat.—^ox^h. Atlantic, Faeroe Channel, John Murray ; Iceland, Krabbe, surface. 



23. Hexalonche seleuci, n. sp. 



Cortical shell thick waUed, covered with numerous short, bristle-shaped spines. Pores of very 

 different size and form, and of a peculiar, subregular disposition, similar to those of Hexalonche 

 geometrica (though in tliis case more regular). Each of the six triangular main spines (which reach 

 nearly the length of the radius) is surrounded at the base by three small roundish pores, and 

 these are further supj)lemented by a coronal of six very large polygonal pores ; the six coronals 

 are separated by irregular rows of smaller pores. Inner shell equal to one-third of the outer. Six 

 main spines pyramidal, as long as the radius. 



Dimensions. — Diameter of the outer shell 016, larger pores 0"03 to 0'04, smaller pores O'Ol to 

 0-02, bars 0-05 to 0-01 ; inner shell 0-05 ; length of the spines 0-08, basal breadth 0-03. 



Habitat. — North Atlantic, Station 354, surface. 



24. Hexalonche sexaculeata, Haeckel. 



Haliomma sexaculeatum, Stohr, 1880, Palseontogr., vol. xxvi. p. 87, Taf. i. fig. 8. 



Cortical shell thick walled, twice" as broad as the medullary shell, and covered with short conical 

 spines. Pores irregular polygonal (mostly hexagonal), twice to three times as broad as the bars; 

 six to eight on the radius. Six spines triangular-pyramidal (not quadrangular), somewhat longer 

 than the radius of the shell. 



Dimensions. — Diameter of the outer shell Oil, pores 0"06 to 0'08, bars 0'03 ; inner shell 0"06; 

 length of the spines O'OY, basal breadth 0-015. 



Habitat, — Fossil in Tertiary rocks of Sicily, Grotte, Caltanisetta. 



