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



Genus 284. Octopyle,^ Haeckel, 1881, Prodromus, p. 464. 



Definition. — Pylonida with trizonal lentelliptical medullary shell, surrounded 

 by two crossed, latticed, cortical girdles ; one smaller (primary) transverse, and one 

 larger (secondary) lateral girdle. Four gates between the two cortical girdles divided 

 by a sagittal septum into eight gates. 



The genus Octopyle comprises those Pylonida whidh are distinguished from the nearly 

 allied Tetrapyle by the development of a sagittal septum, dividing the four gates of 

 the latter into eight separate gates. The septum begins with the formation of two axial 

 rods or columellse, which afterwards become branched ; the branches communicating 

 one with another and with the middle parts of the lateral gii'dle (on the poles of the 

 principal axis), there is formed a latticed septum in the sagittal plane, which separates 

 more or less incompletely the right and left halves of the shell. The four gates of 

 Tetrapyle become halved by this septum, and their number doubled. 



Subgenus 1. Octopylissa, Haeckel. 



Definition. — Cortical shell smooth or thorny, but without larger symmetrically 

 disposed spines. 



1. Octopyle ovulina, n. sp. 



Cortical shell lentelliptical, smooth, without thorns. Lateral girdle elHptical, one and a 

 third times as long as broad. Transverse girdle narrow, with two pores on the isthmus (or on 

 the narrowest part of each quadrant). Sagittal septiun as long as the elliptical medullary shell. 

 Eight gates egg-shaped. 



Dimensions. — Length of the medullary shell 0-05, breadth 0'035 ; length of the cortical shell 

 0-16, breadth 0^12. 



Habitat. — Pacific, central area, Station 274, surface. 



2. Octopyle quadrata, n. sp. 



Cortical shell thorny, nearly square, of equal length and breadth. Lateral girdle quadrangular, 

 with rounded edges, of equal length and breadth. Transverse girdle narrow, with three pores on 

 the isthmus. Sagittal septum of the same length as the subspherical medullary shell. Eight gates 

 nearly circular. 



Dimensions. — Diameter of the medullary shell 0'04, of the cortical shell 0'14. 



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



■" Oc(op2/fe = With eight gate-openings ; oktu, 7riix». 



