ISOPODA. 21 



The second antenna also has a peduncle of three joints which progressively 

 decrease in stoutness but increase in length. The multi-articulate flagellum is of 

 some length. 



The mandible is very strong and provided with a four-jointed palp. That 

 of the left side of the animal has a straight cutting edge, bevelled anteriorly and 

 posteriorly prolonged into a stout spur of some length. The cutting edge is hollowed 

 out internally to receive the mandible of the opposite side, here there is no spur, 

 and the cutting edge is cleft to form two very stout teeth. This is as examined 

 in .titii. The palp is four-jointed, but the first is extremely short, the proportions of the 

 others being 5. 7 '5. 3 '5. The second joint has the distal half of its external border 

 provided with somewhat specialised setae, the longest are at the beginning of the 

 series, and speaking broadly there are only two sizes. The terminal joint is curved, 

 fringed throughout its inner border with stout setae ; these gradually increase in length 

 distally and the joint terminates with three long ones. 



The first maxilla (fig. 2) has a small but irregularly shaped masticatory lobe ; 

 its outer border projects forward as a broad lobe, its inner and lower border, which is 

 rounded and considerably larger, bears three very large spinous processes ; of these 

 the most posterior is longest and most slender ; each has a thick tuft of fine setae 

 about the middle of its length where the spine is distinct as such from its basal 

 process. The outer lobe is large, arched towards the middle line, its margin there being 

 almost straight. This is armed with eleven very strong spines though their length 

 and strength is variable. At the lower inner angle there are two small spinous 

 tubercles, one bearing five small spines arranged like the prongs of a fork, the other 

 has only two spines. 



The second maxilla (fig. 3) has a short and broad masticatory lobe ; this has a 

 slightly rounded internal margin armed with numerous long and strong setae. Three 

 setae near the posterior angle are very much longer than any of the others, and 

 become plumose by the presence of hair-like structures. The remainder of the setae 

 do not vary greatly in size, and all except those near the anterior angle are, to some 

 extent at least, plumose. Two lobes arise from the outer part of the masticatory lobe, 

 the inner one is the broader and of an elongated ovoid form ; the inner border and 

 distal extremity is provided with long and stout simple setae of two distinct sizes, and 

 form two rows along the inner margin. The outer lobe is narrow and terminates 

 with four long simple setae and two smaller ones. 



The maxilliped (fig. 4) is remarkable for the disproportion between the 

 masticatory portion and the palp. The former comprises a short but stout joint, 

 the inner margin of which is rounded proximally, and this is followed by another 

 short joint which has a straight inner margin, and from its distal inner angle it 

 slopes rapidly to a much shorter slightly rounded external margin ; tin 1 inner distal 

 margin carries four stitl' plumose sehe, and near these is a single prominent tooth. 

 It is behind this that the first joint of the five-jointed palp lies. The joints of this 



