1426 THE VOYAGE OF H.M.S. CHALLENGER. 



pleon having the postero-lateral angles somewhat squared, the second having them more 

 acute, the third having a very convex lower margin curving up to an acute apex, between 

 which and a less produced dorso-lateral tooth on either side there is a sharp re-entering 

 ansrle : the fourth segment is longer than the coalesced fifth and sixth, and its hind 

 maro'hi forms an obtuse angle at the centre. Viewed from the front the detached head 

 has a balloon-like appearance, the mouth organs representing the narrow lower end. 



The Eyes cover most of the head, leaving free a small space near the horns, and a 

 narrow lateral tract dividing the upper from the lower group of ocelli, except along the 

 1 iack of the head ; the ocelli of the upper group are the larger. 



Upper Antennae. — Under pressure the horns of the specimen have assumed a jointed 

 appearance, from accidental folding of the skin ; some such appearance as this may have 

 led Milne -Edwards to suggest that these horns represented the upper antennas. There 

 can, however, be no doubt that Mr. Spence Bate is right in regarding as the upper antennas 

 the organs placed just behind and below the horns ; these, in our specimen, have two 

 free joints, the first not longer than broad, the second conical, a little bent, twice as 

 long as its greatest breadth, with ten or twelve cylinders spreading out from the inner 

 side and the apex. In a male specimen, taken off Malta by Dr. Bruce, the horns are not 

 acute ; the first joint of the peduncle of the upper antennas is tumid, the two following 

 joints much narrower than the first and not so long as broad ; the first joint of the 

 fiagellum is fringed with filaments on the lower margin and apex, being produced beyond 

 the short second joint ; the third joint is longer than the second, and as long as the 

 upper margin of the first ; there are eighteen other joints, several of the upper ones 

 being distally widened, while the lower are filiform ; the ends of the antennas being 

 broken, the full number of joints was not ascertained. 



Lower Antennae, — These are wanting in the female. In the male specimen from 

 Malta the lower antennas are present, projecting from the lower part of the front of the 

 head, therefore at some distance below the upper pair ; the peduncle is not very stout ; of 

 the three free joints the third is nearly as long as the two preceding together ; the filiform 

 fiagellum has thirty-three joints, of which the first is the stoutest, though itself abruptly 

 narrower than the peduncle ; the joints at the middle of the fiagellum are the longest. 



Upper Lip very small, distally narrowed, with a rather wide emargination, one of 

 the lobes thus formed appearing to be minutely (perhaps accidentally) bifid. 



Mandibles rather long and narrow, the cutting-edge nearly straight, striated, and 

 very finely denticulate, with a prominent tooth at each corner; there is a spine-row of 

 several very small spines and a long molar tubercle the crown of which is covered with 

 a brush of numerous small spines. Neither in the specimen here described nor in the 

 male specimen from Malta was there a mandibular palp. 



Under Lip. — The principal lobes ciliated, the mandibular processes smooth, con- 

 nected with the other lobes by a very convex outer margin. 



