REPORT ON THE AMPHIPODA. 925 



it is in reality a mark of distinction on which great stress ought to be laid, is a matter 

 still open to inquiry ; in small specimens it does not lend itself very readily to the 

 determination of the species, but its intrinsic importance cannot be judged by the student's 

 convenience. But for the upper lip the present genus might be united with Halirages. 



Atylopsis magellanicas, n. sp. (PI. LXXIX.). 



Head angled in front, with no proper rostrum ; the first three segments of the pleon 

 with the postero-lateral angles acute, a little outdrawn in the second, and more decidedly 

 in the third, the hind margins sinuous. 



Eyes rather large, reniform. 



Upper Antenna?. — With the first joint longer and thicker than the second, but neither 

 very long ; the rest of these appendages was missing. 



Lower Antennae. — First three joints very short, the fourth shorter than the first of 

 the upper antennae ; the rest missing. 



Upper Lip with the distal end broadly and flatly rounded, with a slight tendency to 

 be unequally bilobed. The figure in the Plate gives only a profile view ; the description 

 was made possible by the dissection of a second specimen after the Plate had been 

 engraved. 



Mandibles short and compact ; the cutting plate short, divided into six or seven 

 teeth, the outermost small, the two next considerably larger ; the inner plate on the left 

 mandible widening distally, the edge divided into five teeth, of which the lowest is the 

 largest ; the secondary plate on the right mandible was not well observed, but appeared 

 to be as usual of slighter build than that on the left ; spine-row of seven or eight serrate 

 spines ; the molar tubercle close to the spine-row, short but prominent, with the crown 

 surrounded by long denticles ; the process close above it is short and conical, and 

 immediately succeeded by the palp, of which the first joint is short, the second broad, 

 slightly concave behind, the surface near the front margin set with a few setae or 

 spines, those near the apex being long ; the third joint is as long as the second, 

 with the outer margin convex, with two spines on the outer surface near the base, 

 the inner margin obtusely angled rather than convex, with three pairs of setiform 

 spines near the centre, followed by five spines, pectinate strongly on two edges, of 

 which the lower two are longer than those which follow, these five being succeeded by 

 five more at the apex, of which the earlier two (especially the second) are stronger and 

 more strongby pectinate than the remaining three. 



Lower Lip. — Principal lobes little dehiscent, inner lobes short but rather thick ; 

 mandibular processes short, squared at the end. 



First Maxillae. — Inner plate oblong, the distal margin truncate, slightly oblique, 

 carrying five plumose setae, of which the innermost is not larger than the one next it, 



