56 THE VOYAGE OV H.M.S. CHALLENCiEK. 



of the second, ochreous yellow. Third genital segment above and lielow browuLsh-black, 

 the disk of the third below and apex reddish-yellow. Antennae : third joint about two- 

 thirds the length of the second, fourth a little shorter than the second. Front tarsus : 

 first joint about one-fifth shorter than the second, which is cleft before the middle. 

 Middle tarsus: first joint two and one-half times the length of the second. 

 J . Length 5, breadth 2, middle femur 6, hind femur 4.5 mm. 



Habitat. — North Atlantic, near St. Helena {Berlin Museum). Indian Ocean, near 

 Ceylon {Oxford Museum). Eschscholtz gives the South Atlantic as the locality of his 

 specimens, and Fairmaire determined some of Coqucrel's Halobates taken near Mada- 

 gascar as belonging to this species. 



$ . Oblong, widest in the middle, then becoming slightly and gradually narrower to 

 each end. Greyish-black in old examples (when fresh " blue-grey, as if covered with 

 bloom "), silvery white on the sides and below. As in the allied species, the usual red 

 spots on the head are very distinct, oblique and transverse, and nearly meet at tlie 

 middle of the hind margin. Antcnnaj and legs brownish or fuscous black. Eostrum 

 shining black. Eyes dark brown. Outer rim of the front acetabula very narrowly, a long 

 triangular black-edged blotch on, and extending in front of, the middle acetabula below, 

 a spot on the outer side of the hind acetabula, the ventral segments of the abdomen 

 (except at the sides, especially of the sixth), the disk of the first genital below, and the 

 under side of the horns of the second genital, ochreous 3-ellow. The third genital seg- 

 ment above brownish-black ; third below brownish-bluck, with the disk and apex reddish- 

 yellow. 



Head moderately convex, the edge of the hind margin distinctly elevated, except 

 near the eyes. Antenncs (PI. II. fig. 2, a.) slender, aljout one-half tlie length of the 

 body ; first joint subequal in length to the three others taken together ; second about 

 one-third the length of the first ; third about two-thirds the length of the second ; fourth 

 subequal to the second, cylindrical, slightly attenuate upwards. 



Pronotum, of the usual shape, disk nearly flat, slightly longitudinally convex in 

 middle, with a very slight hollow on each side of the middle. Mesonotum. slightly 

 widened to the middle, disk rather flat. 



Front legs : femora moderately thick, thickest a little above base ; til)ia about four- 

 fifths the length of the femur ; tarsus (PI. II. fig. 2,/.t.) more than one-half the length of 

 the tibia, first joint about one-fifth shorter than the second, which is cleft bt'forc the middle. 



Middle legs : femur shorter than the tibia and tarsus taken together, armed with fine 

 spines ; tibia three-fourths the length of the femur, armed like the femur ; tarsus (PI. II. 

 fig. 2,m.t.) about one-half the length of the tibia, first joint about twn and one-half timos 

 the length of the second. 



Hind legs : femur not quite twice as long as the tibia and tarsus together, armed 



