6 4 



furca is contained three and one-third times in the total length of the cepha/othorax, from the 

 frontal margin to the base of the genital segment. The genital segment is decidedly longer 

 than the combined length of the next two segments. There is a well defined spine on the 

 middle of the right side, and a curved spine on the right of the genital opening. The posterior 

 margin of the segment is fringed with fine spines. The second segment is about half as long 

 as the first. The third segment is shorter than the second, and the fourth segment is shorter 

 than the third. The furcal joints are about half as long as broad, and are equal to fully half 

 the length of the anal segment. 



The antennules are twenty-three-jointed, and extend to the end of the second abdominal 

 segment. 



The antennae, mandibles, maxillae and maxillipedes, are similar to those of Undeuchaeta 

 plumosa. 



The exopodite of the first pair of feet is two-jointed, and there is no outer-edge spine 

 on the middle of the first joint. 



The endopodite of the second pair of feet is one-jointed. 



The third and fourth pairs of feet have a three-jointed exopodite and endopodite. The inner 

 margin of the first joint of the basiopodite of the third pair of feet is furnished with a fringe of fine 

 hairs. The inner margin of the first joint of the basiopodite of the fourth pair of feet is naked. 



The male is unknown. 



Occurrence. — Eighteen females were found in plankton collected at the following stations. 



Stat. 141 (HENSEN vertical net 1500 metres to surface), 4 specimens. — Stat. 142, 2 speci- 

 mens. — Stat. 215% 2 specimens. — Stat. 243 (HEXSEX vertical net 1000 metres to surface), 

 5 specimens. — Stat. 276 (HEXSEX vertical net 750 metres to surface), 5 specimens. 



This species appears to be an intermediate form between Undeuchaeta major, and 

 Vndeuchacta plumosa. It is distinguished from the former by the absence of the high crest on 

 the forehead, and from the latter by the spine on the right of the genital opening, and also 

 by the faint crest. 



6. Family Euchaetidae. 

 Genus Euchaeta Philippi, 1843. 



In this report, the Euchaeta marina type has been separated from the Euchaeta norvegica 

 type, on account of distinct differences in the character of the fifth pair of feet of the males, 

 and also in the armature of the apical spines on the first maxilliped of the female. 



Euchaeta marina (Prestandrea) appears to be the first known member of the genus 

 Euchaeta established by Philippi in 1852, and the characters of the appendages of the two sexes 

 are, therefore, regarded as typical of the true Euchaeta. The armature of the spines on the apex 

 of the first maxilliped of the female, and the structure of the male fifth feet in Philippi's type, 

 are decidedly different from what are found in Euchaeta norvegica Boeck. These differences are 

 now made the distinguishing characters of the two genera, as established in the present report. 



64 



