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



Dimensions. Length of the cortical shell 0'24, breadth - 18 ; thickness of its wall O035 ; 

 diameter of the medullary shell - 06. 



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



5. Spongodruppa elliptica, Haeckel. 



Acanthosphcera elliptica, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. 

 vii. fig. 4. 



Cortical shell nearly twice as long as broad, four times as broad as the ellipsoidal medullary 

 shell Spongy framework compact, with small meshes. Surface covered with very numerous 

 short radial spines, about as long as the medullary shell. 



Dimensions.- Length of the cortical shell 0'2, breadth O'll ; length of the medullary shell 

 0-04, breadth 0'03. 



Habitat. Philippine Sea, Ehrenberg, Station 206, depth 2100 fathoms. 



6. Spongodruppa polyacantha, Haeckel. 



Haliomma polyacanfhum, J. Miiller, 1858, Abhandl., p. 36, Taf. i. figs. 10, 11. 

 Haliomma polyacanthum, Haeckel, 1862, Monogr. d. RadioL, p. 430. 



Cortical shell one and a third times as long as broad, twice as broad as the ellipsoidal 

 medullary shell. Spongy framework loose on the surface, with large regular meshes. Surface 

 covered with fifteen to twenty thick, conical spines, about as long as the radius of the shell. 



Dimensions. Length of the cortical shell - 12, of the medullary shell 0'09 ; diameter of the 

 medullary shell 0'05 to 0'06. 



Habitat. Mediterranean (south coast of France) ; Atlantic (Canary Islands), Station 354, surface. 



Genus 149. Spongatractus, 1 n. gen. 



Definition.- S pongurida with spongy ellipsoidal cortical shell, enclosing a 

 simple, spherical or ellipsoidal, latticed medullary sheD. On the poles of the axis occur 

 two opposite strong spines. 



The genus Spongatractus differs from Spongodruppa by development of two strong 

 spines in the axis of the shell, on its two opposite poles ; therefore it bears the same 

 relation to the latter that Lithatractus does to Druppula, and can be derived from 

 LithaJractus by a spongy thickening of the cortical shell. 



1 . Spongatractus pachystylus, Haeckel. 



SpongospJicera pachystyla, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 82, 

 Taf. xxvi. fig. 3. 



Cortical shell one and a half times as long as broad, with rough surface. Spongy framework 

 compact, with small meshes, about as thick as the spherical medullary shell. Polar spines very 



1 Spongatractus- Spongy -spindle; 



