5G THE VOYAGE OF H.M.S. CHALLENGER. 



In the maxillipedes {fig. 8) the stipes and lamina are not separated by a complete 

 suture. 



The second pair of thoracic appendages in the male are modified like those of all other 

 species ; the inner side of the second, third, and fourth joints is clothed with fine delicate 

 hairs (PI. IV. fig. 6) similar to those of Serolis necera, but more delicate and incon- 

 spicuous ; these structures I was only able to find in some of the specimens from Stations 

 168 and 169; in the large specimen from Station 15G ((_/! PI. IV. fig. 5) they are cer- 

 tainly not present, nor in the single specimen from Station 164a. It does not appear 

 quite certain whether the presence or absence of these hairs is merely a local variation or 

 an indication of a dimorphism in the males of this species analogous to that which Fritz 

 Miiller^ has described in a species of Tanais. 



The remaining thoracic appendages are slender, like those oi Scrolls gracilis, and, as in 

 that species and others, the fourth joint is longer than the third or fifth joints ; the hairs 

 and spines are also small and delicate ; neither the serrated spines found in many species 

 nor the pinnate hairs found in Serolis necera and 'Serolis gracilis seem to occur in this 

 species ; at the distal end of the penultimate joint only are there very long slender hairs, 

 many of which are considerably longer than the terminal joint of the appendage. 



The abdominal ajypendages are like those of Serolis antarctica. 



The operculum is divided by a transverse suture at right angles to its longitudinal 

 axis. 



The uropoda are comparatively small, and attached at the commencement of the 

 posterior third of the caudal shield. 



Variations. — The description just given refers to two specimens dredged at Station 

 156 ; this species was also obtained at three other Stations, viz.. Stations 164c (400 fathoms), 

 168 (1100 fathoms), and 169 (700 fathoms), and some of the specimens show certain 

 difi"erences, chiefly in the length of the posterior thoracic epimera and in the conformation 

 of the two abdominal epimera ; in one specimen (PI. IV. fig. 3) the posterior thoracic 

 epimera, instead of lying nearly parallel to the long axis of the body, are curved inwards 

 towards the extremity so as to partly enclose the caudal shield ; in this specimen the last 

 thoracic epimera are proportionately longer than in the type sjjecimen, measuring 36 mm. 

 as against 35 mm. length of body, whereas in the type specimen these epimera, as already 

 stated, measure 47 mm., the length of the body being 54 mm. In the majority of speci- 

 mens the abdominal epimera terminate in a sharj) point and are not notched at their 

 extremity; two other specimens, however, had abdominal epimera precisely like those figured 

 on PL IV. fig. 1, and since both these specimens are small, not measuring more than half 

 the length of certain other specimens in which the abdominal ej^imera terminate simplj- 

 in a point, this character cannot be looked upon as peculiar to adults. 



In all the specimens obtained at Stations 168 and 169, the ridges upon the cephalic 



' Fiir Darwin (Facts for Darwin), Euglish translation, London, 1869, p. 19 ct seq. 



