30 THE VOYAGE OF H.M.S. CHALLENGER. 



considered peduncle and what flagellum ; the first two joints of the peduncle are of equal 

 length, but the second is more slender than the first ; the difference in size between them 

 is, however, much less than is ordinarily the case ; the third joint is very much narrower 

 and shorter than the second, and the fourth smaller still ; the two joints of the flagelluin 

 are subequal and a little longer than the terminal joint of the peduncle. 



The antennw (fig. 9) have a peduncle consisting of six joints ; the first two are subequal 

 and very short ; the third is rather more than twice the length of the first two taken 

 together ; the fourth is again short, about half the length of the third joint ; the fifth 

 joint is as long as the third and fourth together, and the sixth is longer still but more 

 slender ; the flagellum consists of about eight joints which are elongated but gradually 

 decrease in length towards the extremity ; the flagellum is a little shorter than the terminal 

 joint of the peduncle. 



The first pair of thoracic appendages are stouter than the succeeding, and are 

 prehensile; the proximal joint (see PI. III. fig. 10) is the longest and at the same time 

 the most slender ; the two following joints are short, stout and subequal ; the 

 following joint is very much broader and at the same time longer than either of the 

 preceding; the fifth joint is of nearly equal length but narrower; the distal joint 

 is extremely narrow and curved, and folds back upon the penultimate joint of the limb. 



The succeeding pairs of limbs are longer and more slender than the anterior pair and 

 are similar to each other in structure. 



The first joint is the longest, the second is not much shorter, the third is of about 

 half the length of the second ; the fourth joint is as long or very nearly as long as the 

 first ; it has a series of spines along the inner margin ; the fifth is much more slender 

 than any of the preceding which are subequal in diameter ; it is about as long as the 

 fourth joint, and like it furnished with a series of stiff hairs ; the terminal joint (fig. 11) 

 is very short and bears a spine about equal to itself in length, as well as a short slender 

 hair which corresponds to the second spine developed here in Munna, J sera, &c. 



The operculum which covers over the gill appendages extends to the very end of t lie 

 pointed extremity of the abdominal shield. 



The uropoda (fig. 13) are small and biramose, the inner branch longer and stouter 

 than the outer. 



Station 149k, off Christmas Harbour, Kerguelen, January 29, 1874; depth, 120 

 fathoms; volcanic mud. 



Pleurogonium serratum, F. E. Beddard (PI. III. fig. 14). 



Pleurogonium serratum, F. E. Bod<lard, Proe. Zool. Soo. Loud, 1^*0, pt. i. \>. 102. 



This second species of Pleurogonium from Kerguelen does not present many 

 differences from Pleurogonium albidum, but appears to belong to a different species. 



