COLLECTED BY CAPTAIN TOYNBEE. 181 



from the apex ; but, whereas in Dana's species the tliree terminal segments diminish in 

 size towards the apex, in the present species tlie apical segment is as long as the three 

 preceding put together. Like Dana, I was unable to satisfy myself as to the form of the 

 appendage. The two terminal setae appear to be shorter than in the species from the 

 Pacific. The basal part of the antenna had moreover only three segments. 



There are four pairs of natatory legs. All the branches had three segments, though in 

 the first pair it was doubtful whether there was any real joint. In all the legs the inner 

 branch was the longer of the two, while in the great majority of the Cyclopoidea the 

 reverse is the case. 



The second and third segments of the a])domen have almost completely coalesced, their 

 original separation being indicated by a distinct indentation. The last segment is deeply 

 bilobed. 



Dana says nothing about the sexual characters in this genus ; and I have had no oppor- 

 tunity of examining a specimen which I knew to be a male. It is moreover quite possi- 

 ble that the present specimen may have been immature. 



It was very active. According to a sketch made at the time by Mrs. Toynliee, it seems 

 to have been of a lightish lilac colour, with green and yellow tints inside, and the eye red. 



Collected April 15, 1858, in lat. 24° 20' S., long. 62° 53' E., at 8 p m. 

 Pl. XXIX. fig. 6 ; fig. 7. anterior antenna, x 60. 



Setella. 

 Setella tenuis, n. s. Corpus 9-articulatum. Antennae anticse crassiusculse, breves, 

 articulis primis duobus subeequis, tertio quintoque longioribus, quarto appendiculato. 

 Maxillipedis digitus fere dimidii articuli secundi longitudine. Styli caudales elon- 

 gati ; setae caudales corpore vix longiores. 



This species differs from S. teniiicornis and S. longicauda in the shortness of the ante- 

 rior antennae and the length of the caudal lamellae, from all the species except S. Acictdus 

 in having only nine segments to the body, and from all in the shortness of the abdominal 

 setae, which are but little longer than the body. I was at first inclined to think that this 

 character ought perhaps not to be relied on, and that the setfe might perhaps be imper- 

 fect; they taper, however, so gradually, and to so fine a point, that they can have lost 

 very little, if any, of their length. 



The deficiency of a segment in this species and in S. Aciculus evidently arises from a 

 coalescence of the first two abdominal segments ; so that the two pairs of appendages are 

 both attached to one segment. The anterior antennae have only six distinct segments, 

 though there are indications of others. The fifth is the longest, then comes the third, 

 while the two basal and the fourth are short and subeqtial. 



The appendage which is, as usual, attached to the fourth segment is rather more than 

 half as long as the apical portion of the antenna. The frontal appendage is shaped as in 

 8. crass? cornis. The caudal lamellpe are elongated. 



The separation of the segments is, however, often so indistinct that I am indisposed to 

 attach much weight to the characters thusafforded. 

 Collected June 26. S. lat. 0° 40' ; W. long. 0° 20'. 

 Pl. XXIX. fig. 12,x30. 



VOL. XXIII. B 2 



