1488 THE VOYAGE OF H.M.S. CHALLENGER. 



both smooth ; third joint a little longer and broader than the second ; fourth longer and 

 narrower than the third ; fifth oval, about as long as the third ; finger apparently- 

 triangular, very sharp at the tip ; all the joints of this limb but the first may be regarded 

 as rudimentary. 



Pleopods. — Peduncles stout, produced downwards at the inner angle ; cleft spine 

 with the arms subequal ; inner ramus with six joints ; outer with seven. 



Uropods. — Peduncles of the first pair longer and broader than those of the second, 

 but not reaching much beyond them, longer than the rami, the lower half of tbe outer 

 margin pectinate ; outer ramus longer than the inner, both acute, strongly pectinate on 

 both margins ; peduncles of the second pair scarcely as long as the outer ramus ; the 

 outer is the longer, very slightly toothed on the outer margin, strongly pectinate on the 

 inner, as the inner ramus is on both margins ; peduncles of the third pair short, the outer 

 ramus much the shorter, with one or two teeth on the outer margin, the inner margin 

 at first smooth and convex, then concave and strongly pectinate, the much broader 

 inner ramus reaching beyond the telson, pectinate on both margins except near the 

 base. 



Telson narrower than the segment with which it is coalesced, about as long as broad, 

 forming in outline an inverted arch, the apex acute. The hexagonal markings conspicuous 

 all over it except just at the tip, where there are some very small submarginal setules ; 

 there is also some extremely minute marginal pectination. 



Length, from front of the head to back of the second pleon-segment, one-fifth of an 

 inch. 



Locality. — July 1875, between Japan and Honolulu; lat. 35° N.; surface. One 

 specimen, male. 



Remarks. — The specific name explains itself. The differences are not very great 

 between this eastern species and the western Ampliithyrus sculpturatus. The sculpture 

 is the same in both. In Claus' species, however, the first joint of the flagellum of the 

 lower antennae does not so nearly equal the last joint of the peduncle as in the Challenger 

 species ; in the second gnathopods Claus figures (though without describing) 1 on the front 

 of the wrist a strong spine of which I here find no trace, while he does not indicate any 

 armature of the thin margin of this and the two preceding joints ; judging by his figures 

 also the fifth and sixth joints in the fourth and in the fifth peraeopods differ from the 

 corresponding parts in the present species ; in the third uropods he gives a more normal 

 outline to the inner margin of the outer ramus, and the telson he figures as having the 

 end broadly rounded, not as in the Challenger species pointed, his description of it being 

 " telson broad and short, rounded off at the end." 



1 It may therefore be an accidental error in the engraving of the plate. 



