DESCRIPTION OF SPECIES 



297 



keel which terminates in a second spine at some distance from the pointed and some- 

 what upturned posterior extremity of the segment. On each side of this median keel 

 there are two lateral oblique ridges, each terminating in a spine some distance from the 

 lateral margins of the segment ; these latter are slightly turned downwards. 



The antennule and the antenna are rather long, the latter being longer than the former 

 and extending back to about the posterior margin of the second free thoracic somite. 

 The first and second joints of the peduncle of the antennule are sub-equal, but the first 

 is somewhat bow-shaped ; the third joint is twice as long as the second and six times the 

 length of the fourth. The flagellum consists of twenty-three joints in the male, but only 

 seventeen in the female ; the terminal joint is very small and bears a group of four stout 

 hairs at its tip : an olfactory seta together with several simple setae are present at the 

 distal end of each joint. The first joint of the peduncle of the antenna is short, the second 

 and third are sub-equal, the fourth nearly twice as long as the second, and the fifth 

 slightly longer than the fourth. Tufts of long setae are present on the outer border of 

 the three distal joints, whilst a few shorter ones are scattered along their inner margins. 

 The flagellum consists of seventeen joints, the terminal one of which is small and bears 

 four delicate setae. 



The mandibles are of the usual type : the form of the cutting edge of both the left and 

 right mandible is shown in the figure (Fig. 6 a). The outer lobe of the maxillula bears, 



Fig. 6. Serolis kempt, n.sp. 

 a, cutting edges of mandible: x 24. b, second thoracic appendage of (J: x 24. c, third thoracic appendage 

 of adult (J: x 24. d, fourth thoracic appendage: x 24. e, eighth thoracic appendage: x 24. /, fourth 

 pleopod: x 15. g, uropod: x 30. 



