304 Prof. J. C. Schiodte on the 



carries seven spines, scattered from the point downwards along 

 the inner margin, of the same description as those of the outer 

 lobe, only a little stouter and shorter. The first pair of 

 maxillffi is especially distinguished by its rudimentary palpus, 

 which does not reach forward beyond one fourth of the outer 

 margin of the outer lobe, and consists of only one conical 

 joint, with two setae on its truncate apex. The outer lobe is 

 narrow, falciform, and carries from the point downwards, 

 along the anterior third of the inner margin, eight long, thin, 

 incurved, very pointed spines arranged in an upper and a 

 lower row, and behind them, further back, four other short and 

 stifi' scattered setse ; the inner lobe of the first pair of maxillae 

 is very small, with three delicate spines at the apex, and 

 reaches scarcely so far forward as the apex of the palpus. 



If now we finally remove all the just mentioned appendages of 

 the mouth, the most remarkable feature of its construction 

 appears, viz. that the middle and lateral lobes of the lower lip 

 are not distinguishable from one another, so that there is 

 really only one lobe on either side, the right-hand one 

 involving to some extent the one on the left side ; in front, 

 the two short, rounded, linguiform apices diverge a little, so 

 that the extreme ends of the mandibles appear between them ; 

 the mandibular springs of the lower lip are narrow, and their 

 ends, which are a little outward-bent, reach not quite to the 

 base of the mandibles. It is clear from this construction that 

 it is here the lower lip which, by its peculiar modification of 

 the shape usual in Gammarini, has been adapted to form the 

 innermost enclosure of the oral tube, whilst the outer lobes of 

 the maxillipeds supply its outer enclosure. If now, finally, 

 the mandibles are laid bare by the removal of the lower lip, 

 their configuration shows not a little similarity to that described 

 in j3^ga. The stipes, on which the palpus is inserted closely 

 in front of its outer corner, is narrow, thinner in front, 

 gradually passing into the very narrow and long outer lobe, 

 whose flat rounded apex carries six minute saw-teeth ; the 

 inner lobe is very small, membranaceous, narrow, terminating 

 in three slender and pointed digitiform lobes. 



A comparison between this combination and the forms of 

 sucking-mouth described above in Isopoda discloses the 

 remarkable difference, that the back wall of the rostrum in 

 LapJiystius is formed by the lower lip to the exclusion of the 

 two pairs of maxillae, of which, therefore, the first has been 

 subject to very little modification, the second to none at all, as 

 compared with the usual construction for biting-purposes ; 

 whilst in sucking Isopoda the back wall of the sucking-tube 

 is formed by the second pair of maxilla^,, whereby the first 



