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



around the principal axis, we reach the characteristic form of Larcospirema, the first 

 subgenus of Larcospira ; but if afterwards the second wing follow the example of the 

 first, and overgrow it from the other side, we reach the typical form of the second 

 subgenus, Larcospironium. In this latter subgenus the spiral becomes double, whilst in 

 the former it remains simple. 



Subgenus 1. Larcospirema, Haeckel. 



Definition. Spiral convolutions or turns of the cortical shell simple ; only one 

 single wing of the transverse girdle turning around the principal axis. 



1. Larcospira lentelliptica, n. sp. 



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

 Perimeter of the lateral plane elliptical, one and a half times as long as broad, without constrictions. 

 One lateral wing of the transverse girdle is more strongly developed and turns around the other 

 in two to three simple spiral turns. 



Dimensions. Length of the cortical shell 0'2, breadth 016 ; length of the medullary shell 0'05, 



breadth 0'04 



Habitat. Pacific, central area, Station 265, depth 2900 fathoms. 



2. Larcospira quadrangula, n. sp. (PI. 49, fig. 3). 



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

 Perimeter of the lateral plane nearly quadrangular, with four rounded corners (on the poles of two 

 crossed diagonal axes), one and a third times as long as broad, with one sagittal constriction at the 

 poles of the principal axis. One lateral wing of the transverse girdle turns around the other in 

 one and a half to two simple spiral turns. 



Dimensions. Length of the cortical shell 018, breadth 01-4 ; length of the medullary shell 0'06, 

 breadth 0'04. 



Habitat. Pacific, central area, Station 274, depth 2750 fathoms. 



3. Larcospira sexangula, n. sp. 



Cortical shell with spiny surface, four times as long as the hexagonal medullary shell. 

 Perimeter of the lateral plane nearly hexagonal, one and a half times as long as broad, with six 

 rounded corners (two on the poles of the principal axis, four on the poles of two crossed diagonal 

 axes), with three slight ring-like constrictions. One lateral wing of the transverse girdle turns around 

 the other in two to two and a half simple spiral turns. 



Dimensions. Length of the cortical shell 0'24, breadth 016 ; length of the medullary shell 0'06, 

 breadth 0'04. 



Habitat. Pacific, central area, Station 271, depth 2425 fathoms. 



