COPEPODA 37 



Scott suggest that Hcterocalanus vicdms Wolf, is identical with Kroyers Calamts cristatus\ 

 this species, of which I have examined the type specimens, 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 plumous setae in distal lobes Alcgacalanus 2. 



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



2. 3 Se of Re III of pes II — IV Megacalatms priiiccps Wolf. 



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



Calanus rohnstior Giesb. 



3. Maxillae 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 densely plumous setae. Re pes I without Se. Front with 2 conical processes 



Bathycalanus G. O. Sars. 6. 



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



Macrocalanus (Hcterocalanus) priiiccps Brady. 



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



Macrocalanus (Brady calanus) typiciis Scott. 



6. Re pes I two segmented. Rostral processes rather slender Bathycalanus Richardi G. O.Ssirs. 

 6. Re pes I with 3 segments. Rostral processes long stiff rounded Bathycalanus maxitnus W o\i. 



3. Macrocalanus princeps Brady. 

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



1S83. Calanus princeps n. sp. Brad}', pp. 36—37, pi. IV 1906 ? Hcterocalanus medius n. sp. Wolfenden pp. 27— 28. 



figs. 3—7. pi. VIII figs. 1-5. 



1904 nee. Megacalanus princeps n.sp. Wolfenden pp. 112 — 113. 



1905. Macrocalanus princeps Brady. G. O. Sars p. 7. 



1905 nee. Megacalanus princeps Brady. Wolfenden pp. 3—5 



pi. I figs. 7—9. 



1906. Megacalanus princeps Brady. Pearson p. 5. 



1908. Megacalanus princeps Brady. Farran p. 21. 



1911 nee. Megacalanus princeps Wolf. Wolfenden pp. 196 — 19S. 

 1911 ? Heterocalanus medius Wolf. Wolfenden pp. 201 — 202 



taf. XL figs. 1-5. 



Description f$. Size. Anterior division 5-5 + 5 mm; posterior 3 mm; total length 13-5 mm. The 

 body 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 which 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 two powerful rounded spines, 

 parallel and directed downwards. At the 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 — , ventrally produced in front, 

 dorsally behind, is distinctly wider and deeper than long, and distinctly twice as long as the following 

 somites. The furcal rami are a little shorter than the third somite and 1-2 as long as wide. 



The antennulae project 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 



