Structure of the Mouth in Sucking Crustacea. 303 



the small frontal horn to the apex of the lobes of the maxilli- 

 peds exceeds by about one fifth the width across the round 

 prominent eyes. The clypeus is of about equal height and 

 width, rather convex, rounded above, the sides being also 

 curved outwards. The upper lip is half as long again as the 

 clypeus, highly convex, with pointed apex, the sides being 

 outward-curved near the base, slightly emarginate towards 

 the apex ; on either side of tbe upper lip a small portion of 

 the stipes of the mandibles appears, whilst their very long and 

 stout palpi lie close to the forehead, ascending on either side 

 of the clypeus ; their terminal joint is very long, one fifth 

 longer than the middle joint, conical, slightly incurved, pointed, 

 furnished with short and long setaj on the apex and along the 

 inner side. The terminal joints of the two palpi cross each 

 other in the margin between the two pairs of antennee. The 

 downward-pointing angle of the facial rhomb is formed by the 

 outer lobes of the maxillipeds lying close to the upper lip, and 

 rolled together one with another. 



If, in the next place, we proceed to dissect the head, beginning 

 from behind, we meet, of course, first the maxillipeds. Their 

 cardines and stipites are prolonged, each pair by itself entirely 

 coalescing, and all together fomiing a club-shaped convex pe- 

 duncle for the terminal parts (lobes and palpi), with rounded 

 base, emarginate sides, and rounded sinuate anterior margin. 

 The outer lobes are considerably shorter than the cardines and 

 stipites together, and lie close together, the inner margin of 

 the left involving that of the right ; they are convex, cup- 

 shaped, with broadly rounded apex when seen together, but 

 each by itself pointedly rounded at the extremity ; the outer 

 margin has close fine hair, whilst the anterior part of the inner 

 margin is finely serrulated with a few shorter setee at the apex 

 and on the under surface. The palpi are very thin, sparsely 

 furnished with setse only at their extremity ; they do not 

 reach forward so far as the apex of the outer lobes, and consist 

 of only two joints of about equal length, of which the terminal 

 one is straight, conical. The inner lol)es of the maxillipeds 

 are very small, not half the length of the outer lobes, conical, 

 with a couple of small seta3 on the rounded apex ; and they 

 are hidden under the inner margin of the outer lobe in such a 

 manner that they do not appear before the maxilliped is 

 turned entirely round so as to show its upper surface. The 

 second pair of maxillffi has the form usual in Gammarini, with 

 two flat lobes, the outer lobe being linear, slightly outward- 

 bent, carrying on its broadly rounded apex seven thin, pointed, 

 slightly incurved spines, ranged in an upper and a lower row; 

 the inner lobe is falciform, shorter than the outer lobe, and 



