﻿38 



COPEPODA 



from the 8 to the 17 segments, but decrease from the 20 to the 24, which is scarcely half as long as 

 the 23, which is of almost equal length to the 25. In the basal segment onl\- 2 terminal setae are 

 observed; the second segment bears three tritheks, and the following 17 segments bear a single one, 

 consisting of rather delicate setae; the 20 — 23 segments have only 2 terminal setae (Sd + "^sthe- 

 tasken"), the 24 segment has a single long and slender seta and the 25 segment has 6. Segment 22 

 has a delicate posterior seta (Sp.) and the two last segments each bear a powerful, ringed plumous 

 one, at least twice as long as the two segments combined. 



Antennae are in the main alike Calanus, but the Si of the Basipodite II is very short and 

 the Re I and II have no Si, but the latter segment has two processes medially. 



Mandibulae: The manducatory part is rather short with the first to the fifth serrations well 

 developed without accessory teeth; the sixth to the eighth serrations are only poorh' developed. The 



four partly plumous setae, of about equal length, are shorter than the width of 

 the segment. The Ri I has only 2 setae and the Ri II has 8 setae anteriorly 

 and a single one posteriorly. 



Maxillulae: The L,e I has the 2 first setae extremely short, almost 

 rudimentary, and the following 7 long and plumous; the Le II is only indistinct 

 without any seta. The Li II, which does not bear any seta, is comparatively 

 shorter than Li III, which is fairly slender with 2 setae only. The Basp. II has 

 2 moderately slender setae (Sp. ?); the Ri I — II which are indistinctly separated 

 from each other as well as from the basipodite, have a single seta each, while 

 extig. 7. j.j^g ^^.j^qj distinguished Ri III bears 4 long and one single rather short seta. Re, 



Alacrocalaniis pnnceps 



Brady, a. Head of adult which lias the usual eleven plumous setae, extends a little beyond the end of 



male. X ^'5. b. Abdomen. ., , ... 



t, q.^ the endopodite. 



X ^ 5* 



Maxillae are in most respects alike Calanus, but the Lob. V bears 

 anteriorly 2 long slender ribbon-shaped setae, and the Ri, which has the articular membranes rather 

 indistinct bears six setae of the described structure. 



Maxillipes: The proportions of Basp. Ic^II, Ba.sp. Ill and Ri = 55:50:30; they are in the 

 main alike Calamts, but Ri II— IV have only a single seta each, and Ri V has 2 Si + i Se. 



Legs are comparatively short and broad and have three segments in exopodites as well as 

 in eudopodites. In the first pair the Re I— II has no Se and the Re III has only a single one, placed 

 a little nearer to base than tip. The Re I— III has i + i + 5 Si (cf. Wolfenden t XI fig. 5, in which, 

 however, the Se Re III is placed distinctly nearer tip than base). The second pair of legs has the 

 Ri extending just be)ond the end of Re II; the Re I— II is i-i shorter than Re III, but r6 as long 

 as the distinctly serrated St.; the Re I— II have each a Se and the Re III has 3. The third and 

 fourth pair of legs are in the main features alike the second pair. The fifth pair of legs is smaller 

 than the others and differs in several respects. The inner margin of the basipodite II and III are 

 almost straight, thus differing distinctly from pes. II, and in a less degree from pes. Ill — IV. The Ri 

 extends beyond the base of Re III to the insertion of Se 2. The Re I— II have each one Se and the 

 Re III has 2; the number of Si is 4 in Re III and i in Re II, but the Si is wanting in Re I. 



Secretory pores are in pes II found on the the anterior surfage at the base of Se Re II 



