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



Dimensions. Length of the central chamber O04, breadth 0'03 ; length of the lateral girdle 

 012, breadth 0'08 ; height of the gates 0'03, breadth 0'06. 

 Habitat. North Atlantic, Station 353, surface. 



11. Trizonium dodecabelos, n. sp. 



Central chamber spherical. Lateral girdle octagonal, nearly twice as long as broad. Four gates 

 hexagonal, one and a half times as broad as high. Nine to ten pores on the half equator, fifteen to 

 sixteen on the half meridian. Twelve radial spines, four in the lateral plane, in pairs on both sides of 

 the poles of the principal axis, eight others opposite in pairs in two crossed diagonal axes. 



Dimensions. Diameter of the central chamber 0025 ; length of the lateral girdle 01, breadth 

 0-06 ; height of the gates 0'033, breadth 0'05. 



Habitat. Pacific, central area, Station 272, surface. 



Subfamily 2. DIPLOZONABIA, Haeckel. 



Definition. P y 1 o n i d a with two concentric systems of fenestrated girdles, 

 lying in two concentric lentelliptical faces (every one system with one to three girdles, 

 lying in one lentelliptical face). 



Genus 282. Amphipyle^ Haeckel, 1881, Prodromus, p. 463. 



Definition. Pylonida with trizonal lentelliptical medullary shell, surrounded 

 by one single (transverse) latticed cortical girdle. 



The genus Amphipyle opens the large series of Diplozonaria, comprising all 

 Pylonida, the shell of which is composed of two concentric systems of latticed girdles; the 

 first system constituting the characteristic " trizonal medullary shell " or " Larnacilla- 

 shell;" the second system composed of one to three girdles of the second order. The 

 first system lies inside, the second outside the central capsule. In Amphipyle only the 

 first (transverse) girdle of the second system becomes developed, and therefore on both 

 poles of the principal axis are two large open gates. Amphipyle repeats the two -winged 

 form of Monozonium ; but whilst the medullary shell in this latter is a simple central 

 chamber, it is here a trizonal Larnacilla-shell. 



Subgenus 1. Amphipylissa, Haeckel. 



Definition. Cortical shell smooth or thorny, but without large, symmetrical!}' 

 disposed spines. 



1 Amphipyle = V?it}i one gate on both sides ; nfi$l, TUX*. 



