AMPHIPOD GENUS LEPTOCHEIEUS. 579 



without apparently noticing the processes *, but this ovei'sight is 

 very easily understood. The integument is so thin that if by any 

 chance, svich as pressure or a Httle mucous dirt collected, the 

 process be flattened against the body, it is impossible to see it. 

 The 4th segment has a group of spines on either side, just above 

 the insertion of the uropods. The processes on the 5th segment 

 extend beyond the very small 6th segment. 



Antennae. Superior Antenna (figs. 1-3). — 1st joint of the peduncle 

 stout, slightly longer than the 2nd in actual measurement, the 

 greater apparent length of the latter being due to its slenderness ; 

 in only one of the specimens, Grube's largest, the 2nd joint 

 was a very little longer than the 1 st ; on the outei- side are 

 several small ciliated hairs, and a cluster of sette with 1 long 

 ciliated hair at the distal angle ; the inner angle carries a very 

 long, stout, outstanding sensory spine with 2 smaller ones inset 

 beside it. The 2nd joint is only half as broad as the 1st, with a 

 cluster of 3 or 4 setae and 1 long ciliated hair on either 

 distal angle. The 3rd joint in all the large specimens I have 

 examined barely reaches half the length of the 2ncl ; in the 

 smallest one it slightly exceeds half the length. The primary 

 Jlagellum is composed of 9-14 joints ; one young ovigerous female 

 2"5 mm. long had 9 joints; a male measuring 6 mm. had 14; 

 Grube's large females 5*5 mm. and 6*25 mm. had respectively 12 

 and 10, the joints in the last -mentioned case being longer than in 

 the other animals examined. Each joint, from the 4th in the full- 

 grown and from the 2nd in the young, to the penultimate, is 

 provided with a very long sensory filament in addition to the 

 small setfe. The accessory Jlagellum is usually 2-jointed, equalling 

 the 1st joint of the primary in length, and is so described by 

 Norman, Delia Yalle, and Walker. All the specimens examined 

 by me, except one, agree in having 2 joints only, though the 

 length varies a little, in the small specimen (fig. 1) being slightly 

 less than the 1st joint of the piimary in length, and in the 

 medium-sized specimen (fig. 2) slightly more. The exception is 

 Grube's largest specimen, which has 10 joints in the primary, and 

 a 3-jointed accessory flagellum equalling the first 2 joints of the 

 primary in length. Costa's observation agrees with this, (19) 

 p. 155, " II filetto composto di dieci articoli finamente pelacciuti ; 

 il filetto accessorio lungo appena quan to due articoli del primario." 

 Grube in his description, (24) p. 403, says : " Bei dem von mir 

 zuerst untei'suchten Exemplar fehlte den oberen Antennen die 



Nebengeissel An einem zweiten Exemplar fand ich die 



Nebengeissel und zwar eine 3-gliederige." The first specimen 

 examined by him (from Lussin-piccolo) had, however, an accessoiy 

 flagellum, a 2-jointed one, but this, in both antennae, had lost the 



* " Quelli del quarto [abdominal segment] in oltre gueniiti di piccole spine lungo 

 il margine dorsale." Costa (19) p. 15. 



" Auf dem Riicken des llten und 12ten Segments vor dem Hinterrande sieht man 

 ein paar Borsten." Grube (24) p. 407. 



