1284 THE VOYAGE OF H.M.S. CHALLENGER. 



Vibilia milnei, n. sp. (PI. CXLVIIIa.). 



This species does not differ greatly in general appearance and structure from Vibilia 

 propinqua. The points of difference displayed by the specimen will be described, it being 

 understood that no specific value can be attached to the characters of the lower antennae 

 and the mandibular palp, since they vary with the age of the animal. 



Upper Antennas. — The large flagellum joint oval, with almost entirely smooth margins, 

 the upper more flattened than the lower ; at the rounded apex the two minute terminal 

 joints rest upon the surface, the apical much the smaller and just projecting. 



Lower Antennas about as long as the flagellum joint of the upper, but much narrower. 

 The first free joint short, the second longer, the third intermediate ; the single flagellum 

 joint tapering, nearly as long as the three preceding together, tipped with a spinule. 



Mandibles. — The secondary plate of the right mandible distally divided into three 

 irregular teeth ; the molar tubercle very prominent ; the third joint of the palp not very 

 slender, the apex abruptly acute. 



Maxillipeds. — The inner margin of the outer plates nearly straight, with only a single 

 .small spine to each denticle; the upper part of the outer margin carrying a single 

 spinule. 



First Gnathopods. — The first joint without spines, the second and third joints each 

 with one spine ; the wrist not longer than the hand ; the hand with a single spine within 

 the convex front margin, the hind margin irregularly pectinate, with few teeth ; the 

 finger not more than half the length of the hand, slightly pectinate. 



Second Gnathopods. — The third joint has five spines on the hind margin, and four 

 on the distal margin, these being straight, not hooked, at the tips ; the process of the 

 wrist is very acute, its margin facing the hand not strongly pectinate ; the hand not 

 closely pectinate, carrying some little spinules dispersed over the breast. 



The first four pairs of perseopods are of shorter, stouter build than in Vibilia 

 propinqua, and in the fourth pair the fifth joint is longer instead of shorter than the 

 corresponding joint of the third pair ; the front margin of the fourth joint of the fourth 

 perseopods has four spines. 



Fifth Perseopods little more than half the length of the preceding pair. The first 

 joint broadly oval, not very much longer than broad, widening at once from a narrow 

 neck, the hind margin rather more convex and shorter than the front, not produced at 

 the back of the short second joint, which is bent up close to it ; the third joint longer than 

 the second, little longer than broad ; the fourth slightly longer and slightly narrower 

 than the third ; the fifth a little longer and a good deal narrower than the fourth ; the 

 sixth almost as long as the fifth, a little narrower, round-ended, with some minute 

 armature round the margin, the other joints being quite smooth or with armature 

 requiring a very high microscopic power for its discernment. 



