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



1. Pylospira tetrapyle, n. sp. 



Cortical shell with thorny surface, five times as long as the lentelliptical medullary shell. 

 Perimeter of the lateral plane elliptical, one and a half times as long as broad. Four internal 

 gates (as in Tetrapyle, between the complete lateral wings of the transverse girdle) kidney-shaped. 

 One principal wing of the lateral girdle turns around the other in one and a half to two simple 

 spiral turns. 



Dimensions. Length of the cortical shell 0'21, breadth 015 ; length of the medullary shell 

 0-04, breadth 0'03. 



Habitat. Pacific, central area, Station 268, depth 2900 fathoms. 



2. Pylospira octopyle, n. sp. (PI. 49, fig. 4). 



Cortical shell with thorny surface, three times as long as the lentelliptical medullary shell. 

 Perimeter of the lateral plane elliptical or nearly hexagonal, with four rounded corners (on the 

 poles of two crossed diagonal axes), one and a third tunes as long as broad. Eight internal 

 egg-shaped gates (as in Octopyle), between the complete lateral wings of the transverse girdle, and 

 two axial beams in the principal axis). One single wing of the lateral girdle turns around the 

 other in two to three simple spiral turns. 



Dimensions. Length of the cortical shell 018, breadth 014; length of the medullary shell 

 0-06, breadth 0'035. 



Habitat. North Pacific, Station 253, depth 3125 fathoms. 



Subgenus 2. Pylospironium, Haeckel. 



Definition. Spiral convolutions or turns of the cortical shell double ; both 

 wings of the lateral girdle turning around the sagittal axis. 



3. Pylospira cymbium, n. sp. 



Cortical shell with smooth surface, seven times as long as the lentelliptical medullary shell. 

 Perimeter of the lateral plane elliptical, one and a third times as long as broad. Four internal 

 kidney-shaped gates between the complete lateral wings of the transverse girdle (as in Tetrapyle). 

 Both principal wings of the lateral girdle turn round one another in two to two and a half 

 double spiral turns. 



Dimensions. Length of the cortical shell 0'22, breadth 017 ; length of the medullary shell 

 0-03, breadth 0'025. 



Habitat. Indian Ocean, Madagascar, Eabbe, surface. 



