Crustacea. 5283 



quite so deep as in A. stirynchus. The rostrum is short, stout and 

 elongate-triangular, with an obtuse point ; the margin is much raised, 

 very distinctly lobulated, and there is a very prominently raised, cen- 

 tral longitudinal line ; between these lines the surface is much sunk. 

 The external raised rostral lines run divergingly backwards to the 

 margin of the gastric region, where they alter their course, and pass 

 posteriorly parallel to each other ; midway between these and on either 

 side of the median line are two other and shorter lines less promi- 

 nently distinct. Along the inner margins of these are single rows of 

 punctures, beside which are others scattered irregularly over the 

 whole of the dorsal surface of the carapace. The first abdominal ring 

 is much smaller than any of the others ; the superior anterior margin 

 is rendered concave by the projection forward of two articulating 

 points, which meet two similar points from the posterior margin of the 

 carapace ; the remaining five rings are much larger, and more fully 

 developed and natatory. The three middle ambulations, or third, 

 fourth and fifth, have each, on either side near the posterior and infe- 

 rior angle, a tuft of stout setae. The middle caudal plate is quadran- 

 gular, with two stout spines on each side of the median line, near the 

 upper and middle third. The second plate is also quadrangularly 

 oval, with a row of spines running down the centre; the external one 

 is similar to the second, but without spines, having only a ridge ; all 

 are fringed with long, closely arranged hair, as well as the central one, 

 at their terminal margins. First pair of legs unequal, robust ; the arm 

 thicker anteriorly, twice as long as broad; wrist triangular; hand 

 thick, with sides parallel to each other, smooth, unarmed; the fingers 

 are short, strong, with a few stiff hairs, and the upper one is deeply 

 grooved on its superior and external surface. The second pair of feet 

 are didactyle, much compressed, and look very powerless ; the arm is 

 as long as wrist and hand, and very hirsute along the lower margin ; 

 the other feet get smaller posteriorly. The eye is small and is 

 covered by the rostrum, beneath which it nestles; below, it is shel- 

 tered by the peduncle and spine of the antennae ; the whole forming 

 a kind of quadrangular recess. The points of difference, then, 

 between this and A. stirynchus are, that in this the rostrum is dis- 

 tinctly lobulated on its margin, that the hand is unarmed on every 

 part, and that the upper and external surface of the moveable finger 

 is deeply furrowed, which is not the case in the other. The peculiar 

 way in which the first abdominal ring is attached to the carapace is 

 very striking, and the ventral edge is quite pterygoid in its form. The 

 posterior margin of the carapace seems, on a lateral view, to be quite 



