THE APPENDAGES, THEIR INTERRELATION AND FUNCTION 309 



the gnathobase and this, if the coxa gnathobase remains rigid, will produce a shearing action. Rotation 

 of the coxa will lead to a biting action of the gnathobases of the bases as well as of those of the coxae. 

 The two apical articles of the three-jointed palp are somewhat flattened transversely. The tip of 

 the palp bears two stout claw-like setae (Fig. 5). These are pectinate on their posterior margins and 

 curve posteriorly towards their tips. One of these claws is equal in length to the palp itself, the other 

 is about two-thirds of this length. Besides these, there is, near by, a more slender seta of about the 

 same length as the shorter claw and also a series of four fine setae of about half this length. A series 

 of setae are present on the anterior margin of the palp. When the palp is folded inwards these extend 

 towards the margin of the carapace. Distally on the middle article is a long stout pectinate seta, which 

 is, however, more flexible than the terminal claws. Its length is such that it extends almost to the 

 apex of the shorter terminal claw. Adjacent to it are two much shorter fine setae. A further short 



0'5 mm 



Fig. 7. C. borealis antipoda. Mouth and first trunk appendages viewed from mid-line; caudal furca in front of tips of trunk 

 appendages shown in outline; armature of setae omitted, mn.b, mandibular basis (gnathobase); mn.e, mandibular exopod 

 (mammiliform appendage) ; tnn.p, mandibular palp (endopod) ; mx l p, palp of maxillule ; mx 2 en, maxillary endopod ; mx 2 ex, 

 maxillary exopod ; tr x ex, exopod of first trunk limb. 



seta arises near the apex of the proximal article. The posterior margin bears a further series of setae. 

 There are two long pectinate setae of the same form as the long anterior one. The first of these arises 

 near the distal end of the middle article and the other from a similar position on the proximal article. 

 Both reach to near the apex of the shorter terminal claw. The middle article bears a shorter fine seta 

 on its posterior distal margin and the proximal article three similar short fine setae distributed along 

 the distal half of the posterior margin. All the finer setae bear fine secondary setules. The articulation 

 of the proximal article of the palp with the basis is provided with lateral cuticular facets which limit 

 its movement to a dorso-ventral direction. The limits of movement allowed by the articulation would 

 seem to be from a position where the proximal article is directed nearly vertically upward from the 

 basis to one with it directed vertically downward. The second and third articles can be extended 

 straight in line with the proximal article or flexed toward the body. The articulation of the articles in 

 series is such that the palp can be extended upwards and outwards, with the terminal claws near 

 the antennal notch of the carapace, or folded downwards and inwards. Due to a slight diagonal 

 setting of the articulation between the basale and the proximal article of the palp, the downward and 

 inward movement is accompanied by a rotation of the palp about its axis, in such a fashion that the 



