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



The genus Staurancistra differs from its ancestral form, Stauroloiiche, in the 

 mmification of the four crossed spines. 



1. Staurancistra quadricuspis, n. sp. 



Cortical shell thin walled, with rough, thorny surface, and irregular, roundish pores, twice to four 

 times as broad as the bars ; six to eight on the quadrant. Medullary shell one-third as large, with 

 regidar, circular pores ; connected with the cortical shell by four crossed radial beams. These are 

 prolonged outside into four strong tliree-sided prismatic spines, nearly as long as the shell diameter, 

 each having three curved branches below tlie distal end. (Similar to Hexancistra quadricuspis, 

 I'l. 22, fig. 11, but with only four spines.) 



Dimensions. — Diameter of the cortical shell 016, of the medullary shell O^OS ; pores of the 

 former 0-06 to 0012, bars 0-00.3 ; length of the spines O'M, breadth 0-012. 



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



Genus 65. Stauroloncliidium,^ n. gen. 



Definition. — S t aurosphasr id a with t-nai concentric lattice-spheres and four 

 crossed simple spines -which are disposed in two different pairs, two opposite being larger 

 than the other two. 



The genus Staurolonchidium has arisen from Staurolonche by the stronger growth of 

 the two opposite spines, the other two remaining stationary ; both spines of each pair 

 equal. 



1. Staurolonchidium artloscelides, n. sp. 



Cortical shell thin walled, with smooth surface, three times as broad as the medullary shell. 

 Pores regular, circular, hexagonally framed, twice as broad as the bars ; eight to ten on the quadrant. 

 Four radial spines three-sided pyramidal, as broad as one mesh ; two opposite larger spines three 

 times as long as the two smaller, which are about equal to the radius. 



Dimensions. — Diameter of the cortical shell 0-16, medullary shell 0-05 ; pores of the former 0-012, 

 bars 0-006 ; length of the major spines 0-24, minor 0-08. 



Habitat. — Central Pacific, Station 265, siu-face. 



2. Staurolonchidium perspicuum, Haeckel. 



Haliomma perspkmim, Ehrenberg, 1875, Abbandl. d. k. Akad. d. Wiss. Berlin, p. 74, 

 Taf. xsix. fig. 1. 



Cortical shell thin walled, covered with small conical by-spines, five times as broad as the 

 medullary shell. Pores regular, circular, eight times as broad as the bars ; three to four on the 

 ([uadrant. Four radial spines three-sided pyramidal, scarcely one-third as broad as one mesh ; two 

 opposite larger spines four times as long as the two smaller, which are about equal to half the radius. 



• StoMroio?icAidmm= Diminutive from Staurolonche. 



