228 DE. C. CHILTON ON THE SUBTEEEANEAN" 



peraeon are all of about the same length and as long as the head ; the first three segments 

 of the pleon are rather longer, their inferior margins bear two or three stout setae towards 

 the anterior end ; the fourth segment of the pleon has a strong spiae on the inferior 

 margiti at the base of the uropod, and each of the last three segments bears four or five 

 long spine-like setae on the dorsal surface. 



The tipper mitennce (fig. 2) appear to vaiy somewhat in length as compai'ed with 

 the body, but they are always very long, usually about as long as the body. The first 

 joint of the peduncle is stout, rather more than twice as long as broad ; the upper margin 

 is straiglit, with a tuft of fine setae at the extremity ; lower margin slightly curved and 

 bearing two short transverse rows of spiniform setae, the second row being situated at 

 the extremity. Second joint about as long as the first, but only about half the width ; 

 upper margin with three or four fine setae ; lower margin with three or four tufts each 

 containing a spiniform seta and one or more fine hairs, at the extremity there are tufts 

 above and below and in the centre. Third joint about one-third as long as the second, a 

 few setae above and below at the extremity. Secondary appendage slender, usually con- 

 taining six or seven joints, though there may be as many as nine, each joint with minute 

 setae at the extremity ; flagelhim more than twice as long as the peduncle, consisting of 

 a great number of joints, the setae on which are very short and fine, each joint bears a 

 single small olfactory cylinder. 



The lower antennce (fig. 3) are more than half as long as the upper. The first joint of 

 the peduncle is very short and bears a single seta at the extremity of the lower margin ; 

 second joint very short, the gland-cone (the so-called "olfactory denticle") not reaching 

 quite to the end of the succeeding joint ; the third joint more than twice as long as 

 the second, upper margin curved, lower margin with a tuft of strong spiniform setae 

 at the extremity ; fourth joint very long, upper surface bearing five tufts of two stout 

 setae each, the lower surface wdth numerous small tufts of stout setae and fine hairs 

 irregularly arranged ; the fifth joint slightly longer than the fourth and narrower, upper 

 surface with about five small tufts, lower surface with five larger tufts of longer setae ; 

 flagellum usually about as long as the peduncle, though the relative lengths vary 

 somewhat ; it usually contains about twenty joints, each bearing a few fine setae at the 

 extremity. 



The tipper Up (fig. 4) is strongly chitinous and of the usual shape, being more or 

 less semicircular, very broad ; the apex bears a thick fur of minute setae, mostly con- 

 verging inwards. 



The mandihles (figs. 5, 6, 7, 8) appear to present a pretty close resemblance to those of 

 Gammarus neglectus as described and figured by Sars. The jialp, which is the same in 

 both mandibles, is large and strong. The first joint is the shortest; it widens slightly 

 distally and bears fom- or five setae at the extremity. The second joint is about twice as 

 long as the first; it is rather broad, and bears on the inner margin about a dozen long 

 setae, those towards the end being the longest. The third joint is somewhat shorter than 

 the second, and bears on the surface of the side four small tufts each containing two 

 setae ; the outer margin is slightly curved and is free from setae ; the inner margin has 

 along its whole length, except a little at tiie base, a thick fringe of stiff setae about half 



