REPORT ON THE AMPHIPODA. 689 



might have been present originally ; the remaining joints short, successively diminishing 

 in length and thickness, many of them carrying long filamentary cylinders ; the secondary 

 flagellum of three slender joints, two long and one very short, the three together not 

 equal in length to the first of the primary. 



Lower Antenna. — The gland-cone prominent, the third joint not much shorter than 

 the composite first and second, the fourth and fifth long, straight, parallel-sided, the 

 fourth rather wider than the fifth, equal to it in length, and also equal in length to the 

 first four joints of the seven-jointed flagellum. 



Triturating Organ. — In the Lysianassidse this organ differs much from the form 

 presented in the Orchestidse. In the present species the oval organ exhibits round one 

 margin a row of some two dozen spines, of which the Ijasal half is thick, the other half 

 becoming abruptly thinner and curved ; round the opposite margin is a still more closely 

 set row of some twenty-eight longer spines, nearly straight, pretty evenly thick all along 

 to the end, which is cut into a short fork ; where the two rows meet at the outer 

 extremity of the organ there are some ciliated spines. 



Mandibles. — Cutting edge smoothly convex, with an upper tooth turned a little 

 downwards and a lower one turned a little upwards ;^ secondary plate on the left 

 mandible small, strap-shaped, its edge cut into four or five teeth ; spine-row consisting 

 of three slightly curved spines (only two present on the right mandible) ; molar tubercle 

 prominent, its oval crown somewhat ciliated on the edges, carrying four or five teeth 

 down the centre, the remainder divided into rows of very minute denticles ; the palp 

 set far forward just over the molar tubercle, the first joint short, the next rather long, 

 with eight or nine spines near the apex ; the third joint shorter than the second by 

 about the length of the first. The pectinate spines on the inner margin of the third 

 joint, beginning below the middle, increase in length to the apex ; they numbered 

 seventeen on the left, fourteen on the right mandible. 



Lower Lip. — With the forward lobes broad, pretty strongly ciliated. 



First Maxillse. — Inner plate smaU, oval, with two plumose setee at the apex, the 

 inner being the smaller ; outer plate large, the apical margin with six strong dentate 

 spines, below which are five others, the outermost strong, little dentate, the others a 

 little more slender, not much curved, each with four or five lateral teeth ; the palp 

 reaching beyond the outer plate, its second joint nearly parallel-sided, the apical 

 margin carrying from nine (on the right maxilla) to twelve teeth (on the left maxilla), 

 the outez'most longest, and one pectinate seta on the surface not far from the outer 

 tooth. 



Second Maxillw. — The outer plate broader than the inner and prolonged a little 

 beyond it ; on the apex and a short way down the inner margin of the inner plate 



' The true shape of this part of the mandibles was not clearly made out till after the figures, PL XII. m. m., had 

 been lithographed. 



