AHT. IS SYNOPSIS OF CALANOID CEUSTACEA MARSH 3 



Family CENTROPAGIDAE 

 Genus LIMNOCALANUS Sars, 1863 



Body long and narrow. The cephalothorax is composed of six 

 segments, is elongated oval in form, with its greatest width at about 

 the middle. The last cephalothoracic segment is not produced lat- 

 erally. The abdomen is slender, composed of three segments in the 

 female and five in the male. The furcal rami are elongated, ciliate 

 on the internal margins; they are terminated by live elongated setae, 

 of which the second from the inside is the longest, and one short 

 slender seta on the inner margin. The external seta is located back 

 of the end of the ramus. The first antennae are 25-segmented, the 

 terminal segment being ver}^ short. 



The right antenna of the male is geniculated and composed of 22 

 segments; of the normal 25 segments, 19 to 21 and 22 to 23 are united. 

 The terminal portion is composed of four or five segments. In L. 

 macrurus and L. johanscni, the t3'pical form of this terminal portion 

 is that shown in Plate 1, Figure 8; the first of the group, the nine- 

 teenth segment of the antenna, is elongated, the second somewhat 

 shorter, the third less than half the length of the second, and the 

 terminal one very short. In exceptional cases in both these species 

 the first segment is divided as shown in Plate 1, Figure 9. In all 

 examined specimens of L. grhnaldii there have been five segments, as 

 in Figure 9. Both Sars (1897) and Willey (1923) give the number 

 of segments as five. 



In the second antennae (pi. 1, fig. 5) the exopod is longer than the 

 endopod and is composed of seven segments, of which the first and 

 the third, fourth, fifth, and sixth are short. All the swimming feet 

 are biramose, the fifth pair both in the male and female differing 

 from the others. Both rami of feet 1 to 4 are 3-segmented, the endo- 

 pods being shorter than the exopods. The outer rami of the fifth 

 pair of the female are 3-segmented, and the second segment is pro- 

 duced on the inner distal angle into a stout curved process. (PL 3, 

 fig. 3.) 



The exopods of the fifth feet of the male (pi. 13, fig. 5) are 2- or 

 3-segmented. The second segment of the right exopod is short, trun- 

 cated, and produced on the inner side into a stout hook. The second 

 segment of the left exopod is elongate, ciliate on the inner border, 

 and in addition to a terminal spine bears three lateral spines on the 

 cuter border. 



