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



sword-shaped, two-edged, of equal breadth, with simple apex. Eight polar spines very short, 

 conical, also with simple apex. Base without leaf-cross, a simjjle pyramid. 



Dimensions. — Length of the four equatorial spines 018, of the eight tropical spines O'l-i, of the 

 eight polar spines 0'04. 



Habitat. — Central Pacific, Station 271, surface. 



2. Belonostaurus bicuspis, n. sp. 



Four equatorial sijines compressed, almost lanceolate in the basal lialf, biiid, with two large, 

 bent, little divergent horns in the distal half. Eight tropical spines nearly of tlie same form, but 

 only half as large, with much smaller horns. Eight polar spines rudimentary, very short, conical, 

 with simple apex. Base with a large leaf-cross. 



Dimensions. — Length of the four equatorial spines 0'2, of the eight troj^ical spmes O'l, of the 

 eight polar spines 0"02. 



Habitat. — Central Pacific, Station 263, surface. 



Genus 336. Lonclwstaurus} Haeckel, 1862, Monogr. d. Eadiol., p. 397 



{sensu emendato). 



Definition. — Q uadrilonchida with four equatorial spines of unequal size and 

 form ; the principal spines (in the longitudinal axis) larger than the lateral spines (in 

 the transverse axis) ; both opposite spines of each pair equal. Sixteen other spines 

 much smaller (often the eight tropical larger than the eight rudimentary polar spines). 

 No apophyses. 



The genus Lonchostaurus differs from the two preceding genera in the unequal size 

 and shape of both equatorial pairs of spines, whilst the two opposite spines of each j^air are 

 equal. Therefore the equatorial plane is here a rhombus, not a sc[uare, as in the preced- 

 ing genera. We encounter here for the first time the differentiation of the two equatorial 

 axes, the longitudinal (or hydrotomical) and the transverse (or geotomical) axis. The 

 sixteen other spines are constantly smaller (often also the eight polar more or less 

 rudimentary). 



1. Lonchostaurus rhomboides, n. sp. (PI. 131, fig. 6). 



Four equatorial spines cylindrical, twice to three times as broad as the sixteen smaller spines, 

 conical at the distal apex ; the two opposite spines of the longitudinal axis twice as long as those 

 of the transverse axis. Sixteen smaller spines conical at the base, with simple bristle-shaped apex. 

 The surface of the rhombical calymma, including the sp)ines, was covered in the figured specimen 

 with small plates like those of Sphcervcapsa. 



Di7nensio7is. — Length of the cross (longitudinal axis) 0"24, breadth (transverse axis) 012. 



Habitat. — South Pacific, Station 302, depth 1450 fathoms. 



' Lonchostaurus = Spear-cross ; 'hiyx.yi, uTavooi. 



