110 2 CRUSTACEA. 



thoracic setae, and also those from base of abdomen, of an orange 

 colour. 



The cephalothorax was broadest just anterior to middle. The 

 caudal stylets were nearly as long as last abdominal segment. The 

 caudal setae were broken off except the outer and two very short at 

 apex, one the inner, the other the outer; there appears to have been 

 only one long seta. The second pair of antennas were apparently 

 simple ; whether the longer setae were naked (as in the figure) or not, 

 is not quite certain. The outer setae of the base of the natatories are 

 slender, and have very short hairs near their tips, which are seen 

 only with a very high power; but the setae are not plumose. 



Another specimen was obtained by the author off Pitt's Island, in 

 which the setae of the base of the natatories were wanting; the cepha- 

 lothorax was more evenly elliptical, and a little more slender, and the 

 outer setae of the caudal stylets were shorter than in the figure given. 



Subfamily PONTELLIN^. 



Many of the Pontellinae (the' Acartiae, Pontellae, and Catopiae) are 

 distinguished from all the other Calanidae by the singular inferior 

 eyes, which form a prominence on the under side of the head; and 

 those not so characterized (the Diaptomi and Candaceae) have the 

 geniculating joint in the male right antenna, as well as a prehensile 

 right leg at the posterior extremity of the thorax. The geniculating 

 joint is wanting in one genus of the Pontellinae alone, Acartia; but as 

 it is possible that none of the individuals observed were males, this 

 genus may be no exception, though we think it not probable. The 

 antennae in Acartia have an unusual degree of flexibility, and we sus- 

 pect that they may therefore be used with the same facility as if the 

 geniculating joint were present. Moreover, the legs of the posterior 

 pair (one-jointed rudimentary appendages with two divaricate setae), 

 even if of females alone (instead of a form common to the sexes), are 

 still unlike anything occurring in other genera; and this divergence 

 is likely to be attended with other peculiarities. 



The general form of the body is similar to that of the Calaninae. 

 The anterior antennae, although they often project transversely, are 

 very often thrown obliquely forward, a position rarely found among 

 the Calaninae. The cephalothorax also is more frequently divided 

 into seven segments than in the preceding groups. 



