14 G. o. saes. [No. 8. 



respiration, is directed obliquely upwards and exhibits along 

 the posterior edge a dense and regular series of very strong, 

 finely plumose setae, about 18 in number, the upmost being 

 however very short; besides from the inferior corner of. the 

 plate, at some distance from the others, 3 or 4 much more slen- 

 der setae, pointing straight downwards, originate. 



The 2nd pair of maxillae (PL .III, fig. 7, PL IV, fig. 

 1) consist of the same principal parts as the 1st, though 

 rather different in appearance. The basal part is considerably 

 smaller and not divided at the end, terminating with a single, 

 somewhat compressed masticatory lobe, that points obliquely 

 forwards. To the obliquely truncated tip of this lobe a consider- 

 able number of delicate curved bristles, successively diminishing 

 in length interiorly, are attached, and besides a single slender 

 ciliated seta is found at some distance from the tip, originating 

 from a distinct ledge of the inner edge. The branchial lamella, 

 attached to the posterior edge of the basal part, is very small, 

 semicircular, and provided with 6 finely plumose and diverging 

 setae. The palp, finally, originating immediately below the bran- 

 chial lamella, is represented by a simple conical lappet, point- 

 ing obliquely backwards and terminating with 3 setae, the 

 middle one much longer than the other two. In the male these 

 maxillae are modified in a peculiar manner to serve for grasping 

 the female during copulation (see PI. IV, fig. 1), the palp being 

 converted into a powerful prehensile organ, which admits of be- 

 ing extended from the shell inferiorly. On closer examination 

 the form of the palp somewhat differs on the right and left 

 maxilla (fig. 4 and 5). In both it is composed of a strong 

 muscular basal part, armed at the antero-inferior corner with 

 a pair of small projections, more pointed of the right maxilla 

 (fig. 4), and a highly chitinised, clawshaped terminal part, mov- 

 ably articulated to the former, and admitting of being impinged 

 against the above mentioned projections. This terminal part is 

 on the right maxilla (fig. 4) lamelliform dilated in the middle 

 and nearly curved at a right angle, whereas on the left (fig- 5 ) 

 it is quite narrow and more evenly curved at the base; on both 



