*3 



Onckocalanus cristatus is easily recognised by the presence of a median cephalic crest, 

 and by the distinct point at the distal ends of the last thoracic segment. The fifth pair of feet 

 ot the female consists of two free joints attached to a basal part. The second free joint terminates 

 in a strong spine. The outer margin of the joint is furnished with two spines and the inner 

 margin with one. Length 6,6 mm. 



Onckocalanus cristatus bas been hitherto only obtained from the deep water of the North 

 Atlantic, where it appears to be not uncommon. 



2. Onckocalanus hirtipes Sars. Plate XXXIV, figs. 9 — 17. 



Onckocalanus hirtipes Sars, 1905 (a), p. 20. 

 Onckocalanus hirtipes Farran, 1908, p. 49. 



One female apparently identical with this species, was obtained from the plankton 

 collected with the Hensen vertical net at Station 185, 1536 metres to the surface. 



Onckocalanus hirtipes has a general resemblance to Onchocala7ius cristatus, but it can 

 be distinguished from it by the absence of a median crest. The last thoracic segment is obtusely 

 triangular in outline when seen from the side, but it is not produced into a spine at the posterior 

 margin. The rami of the rostrum apparently terminate in a filament, but only the base was 

 visible in the preparation. The fifth pair of feet is somewhat similar to that of the previous 

 species. There is only one outer-edge spine on the second free joint and none on the inside. 



Length — 5 mm. 



This species has only been recorded from the North Atlantic. 



Genus Cornucalanus Wolfenden, 1905. 



This genus was established by Wolfenden in 1 905 for a Calanoid closely related to 

 Xantlwcalanus. It is distinguished by the possession of a cephalic spine, and the apex of the 

 first maxillipedes is furnished with a ver}- powerful curved claw. 



The cephalic spine may only be a specific difference between Wolfenden's type species 

 Cornucalanus niagnus (= Scolccithrix chelifcr I. C. Thompson, 1903) and another form very 

 briefly described along with the type. The appendages of the second species are identical with 

 those of the type, but the cephalic spine is absent. 



A form apparently identical with Wolfenden's second species was found in the plankton 

 collected by the 'Siboga'. 



1. Cormualanus simplex Wolfenden. Plate XXXY, figs. 1 — 9. 



Cornucalanus simplex Wolfenden, 1905, p. 22. 

 Cornucalanus simplex Sars, 1907 (a), p. 14. 



Female — length 5 mm. 



Yiewed from above, the body appears moderately robust, and elongate ovate in outline. 

 The head is separated from the first thoracic segment. The fourth and fifth thoracic segments 

 are completely separated. The last thoracic segment is produced posteriorly into points. Seen 

 from the side, the forehead is only slightly arched, and no tracé ot a cephalic spine can be 



83 



