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



posterior of M-hich is the longest aud finely ciliated. The palp, ^-hich is affixed to the 

 outer side of the basal part close to the base of the exterior masticatory lobe, is very 

 elongate and narrow, turned straight backward, and projecting within the branchial 

 cavity. It is uniarticulate and linear in form, with a distinct muscular band running 

 throughout its axis ; from its tip two peculiar compressed seta3 originate, the outer being 

 somewhat longer than the inner, and both having one of its edges sharpened and armed 

 with fine recurved hooks. 



The second pair of maxillse (fig. 10) are more membranous in structure and of a 

 rather different appearance. The basal part is composed of two segments, the first of 

 which is very short and filled by strong muscles. The second segment is almost 

 triangular, and exhibits on the inner side two very slight masticatory expansions, the 

 anterior one somewhat obliquely truncate and provided with short ciliated bristles, the 

 posterior having a regular series of slender seta3 arranged in a combdike manner. From 

 the lower side of the basal part, close to its apex, a very short biarticulate palp originates, 

 directed anteriorly and movably articulated. The last joint of this palp is obliquely 

 truncate at the tip and armed with a dense row of slender curved spines, and the first 

 joint is on the inner side expanded to a lobe of quite a similar appearance. Moreover, 

 the outer edge of the basal part forms a very thin and pellucid expansion, which may be 

 regarded as homologous with an exognath; this expansion has the edges quite smooth, 

 without any trace of bristles. 



The maxillipeds (fig. 12), which are closely applied against the other masticatory 

 parts, and themselves partly covered liy the two pairs of gnathopoda, form each a rather 

 stout and somewhat compressed stem, contiguous with the one of the other side, and 

 having the outer part slightly incurved. The basal part is rather large, occupying half 

 the length of the stem, and consists of two segments, the first of which, however, 

 is very short and rather difficult to see. At the end this part projects inwards 

 as a rounded triangular masticatory lobe, armed at the tip with a few short and thick 

 spines densely cdiated in their outer part. Along the inner edge there also occurs a 

 series of five rather strong plumose setae, and another strongly ciliated seta is found at 

 the base of the masticatory lobe. The terminal part of the stem, or the palp, 

 is composed of but four distinctly defined joints, of which the two first are very broad 

 and lamellar, and connected by a very oblique articulation ; the outer of these latter 

 joints is armed along the inner edge with a series of small, curved, bidentate spines 

 (fig. 12, a), besides numerous fine bristles, and has at the end externally a strong 

 anteriorly curving seta. The two last joints become suddenly much smaller and more 

 or less incurved ; the penultimate is provided at the end with three ciliated setae (two 

 on the inner and one on the outer side) ; the terminal joint is very small and tipped with 

 three or four short bristles. 



At the base of these limbs the remarkable branchial apparatus is affixed (sec fig. 1 1 ). 



