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Scott suggest that Ilcferocalaiius iiicdius Wolf, is identical witii Kroyers Calaniis crisfatus; 

 this species, of which I have exaniiiied the type speciniciis, is however a true Calanus (of. p. ii). 

 On account of the existing confusion I think the following synoptic key will be useful. 



I. Strong hook on anterior surface of hasp. Ill pes. i; pes I — IV with 3 segmented Re and Ri. The 

 maxillae without densely pluiuous setae in distal lobes Mcgacalanus 2. 



1. Strong hook on anterior surface of hasp. Ill pes I wanting 3. 



2. 3 Se of Re III of pes II~IV Mcgacalaniis prhtccps Wolf. 



2. 2 Se of Re III of pes II — IV Calanus gracilis Dana. 



Calami s robuslior Giesb. 



3. Ma.xillae without densely plumous setae. 2 vSe of Re III of pes II — IV Calanus 



3. Maxillae with densely plumous setae. 3 Se of Re III of pes II — IV 4. 



4. Maxillipeds with slender setae Macrocalanus. 5. 



4. Maxillipeds with densel}' plumous setae. Re pes I without Se. Front with 2 conical processes 



Bathycalaniis G. (). Sars. 6. 



5. Frontal crest. Rounded lateral corner. Pes I has no Se in Re I — II, one Se in Re III 



Macrocalanus (Hctcrocalaiius) priiiccps Brady. 



5. Frontal crest wanting. Pointed lateral cornes. Pes I has i Se in Re I — II, 2 Se in Re III 



Alacrocalaiiiis ( Bradycalaiius) iypicus Scott. 



6. Re pes I two segmented. Rostral processes rather slender Bathycalaiius Richardi G. O. Sars. 

 6. Re pes I with 3 segments. Rostral processes long stiff rounded Batliycala)ius maxivius'SS oM. 



3. Macrocalanus princeps 15 r a d y. 



(PI. I figs. 2 a-- b; textfigs. 7 a— b). 



iSi>3. Calanus princeps n. sp. Brady, pp. 36—37, pi. IV 1906 ? Ileterocalanus nic-dius n. .sp. \V<iltVn<Kn pp. 27- 2S. 



figs. 3-7. 1>1. Vlir figs. I -5. 



1904 uec. Mugacalanus princeps n. sp. Wolfenden pp. 112 — 113. 190S. Me.gacalanns princeps Brady. l''arran p. 21. 



1905. Macrocalanus princeps Brady. G. O. Sars p. 7. 191 1 nee. Megacalanus princeps Wolf. Wolfenden pp. 196 — 19S. 



1905 uec. Megacalanus princeps Brady. Wolfenden pp. 3 — ,s 191 1? Heterocalanus niedius Wolf. Wolfeiulen pp. 201— 202 



pi. I figs. 7—9. 1 taf. XL, figs. 1-5. 



1906. Megacalanus princeps Brady. Pearson p. 6. | 



Description f$. vSize. Anterior division 5-5-|-5nnu; posterior 3 mm; total lengtli 13-5 nim. Tlie 

 bod)- is slender, as the anterior division is about 2'5 as long as wide. The first as well as the fifth somite, 

 the lateral corner of wdiich is regularly rounded (fig. 7 b), are well distinguished. The head has a low- 

 crest terminated by a small frontal process. The rostrum consists of tw-o powerful rounded spines, 

 parallel and directed dowuward.s. At tlie base .slender rostal filaments protected above by low pro- 

 cesses. The hinder margin of the head has dorsally a .small elevation bearing a conical process. The 

 urosome consists of four somites, of which the first — the genital one — , venlrally produced in front, 

 dorsally behind, is distinctly wider and (kei)er than long, and distinctly twice as long as the following 

 somites. The furcal rami are a little shorter than the third somite and i-2 as long as w-ide. 



The antennulae ])roject at least 6 segments beyond the tip of the furca; they consist of 25 

 segments, of which, however, the 8 and 9 are less well separated. The .segments increase in length 



