6 COPEPODA 



In front of the labrnm a sometimes hairy protuberance is found; this was by Sars in Euchcete 

 designated the epistoma\ I have in this paper followed him, where the organ belonged to the somite 

 of the antennae. The labrnm proper, which is placed in the mandibular somite is often subdivided 

 and has in the Euchcetidae and Scolecithricidae its free or anterior surface more or less hairy, in a 

 way that often is of systematic importance (cf. pi. VI fig. 2 b, 7 a, 14 a and pi. VII fig. 5 e, 9 b and 



7 c); along the hinder margin of the labrum, separating the anterior and the oral surface, marginal 

 bristles are always observed (pi. II fig. 3 b; pi. IV fig. 5 e). The oral surface is adorned with a more 

 or less developed chitinous framework, to which longitudinal muscles are fastened; this system is by 

 comparison with fig. 7 f. pi. II and fig. 2 a and 5 e pi. IV seen to be differently developed in the different 

 forms. Along the median line three central circular spots, in the middle with two parallel lines, as well 

 as a fourth more posterior one, with a lateral one on each side are found; laterally a few spots, which 

 may perhaps be regarded as muscular spots, are observed (cf. pi. IV fig. 5 e). About the nature of 

 these four central circular striated spots I do not know anything; they are certainly not muscular 

 spots, perhaps sensory ones. Around or behind the fourth spot a bigger or smaller transverse row 

 or area of spines or bristles is observed; the systematic importance may be realised by comparing 

 fig. 2 a and 5 e pi. IV The oral surface of the labrum is on each side near the middle adorned with 

 a lateral longitudinal series of bristles or spines, which is again dissolved into five groups, the more 

 detailed variations of which show interesting differences between species and genera, as seen in 

 numerous figures (pi. I — VII). 



The labium is gradually fused with the posterior wall of the pharynx; it is generally adorned 

 with curious structures. In the middle a compactness in the chitinous skeleton the ^lamina labialis 1 is 

 found; in front it is not well separated from the wall of the pharynx, but its hinder margin seems to 

 be partly free, and shows many variations, as seen by comparing the figures (pi. II fig. 7 f , 2 a and 

 3c; pi. Ill fig. 5e; pi. V fig. 26; pi. VI fig. 3b, n b and 13 b); in the Scolecithricidae this organ seems 

 to be wanting or poorly developed (pi. VII fig. 4 e and 7 d). 



Laterally to the lamina labialis on each side a longitudinal row of 6 generally well articulated 

 spines is found. I have designated it the serrula sexdentata, and as it was found in all the examined 

 genera except Candacia and Heterorhabdus within the Calanoida, but not in any of the few genera 

 of other groups, which were examined, it is certainly of some systematic importance. In front of the 

 lamina labialis and the serrula, curved longitudinal rows of bristles or granules are found, which as 

 seen in the figures show specific as well as generic differences (pi. I fig. 1 c; pi. II fig. 2 a; pi. Ill 

 n g- 5 e > pl- IV fig. 1 c, 2 c and 3d; pi. V fig. 2 b and 4 c; pi. VI fig. ib, 2d, 3 b, 5 a and 10 b and 

 pi. VII fig. 2 c, 4 e and 12 c). Behind the lamina labialis, more or less well developed areas, covered 

 with granules or spines are found (pi. II fig. 7 f.). The labial lobes as well as the area between and 

 behind are covered with series of delicate hairs; the arrangement of these series is different in the 

 various genera, but these differences are probably modifications only of a general system (cf. pi. II 

 fig. 7 f ; pi. IV fig. 1 d, 4 c and 5g; pi. V fig. ic and 5 f ; pi. VI fig. 5 b). Behind the area labialis in 

 the maxillular and maxillar somites an intricated system of hairy areas is sometimes found, f. inst. in 

 Calanus hyperboreus (pi. I fig. 1 d). 



In the literature I have found a good descpription of these organs in Laophonte and Hersiliodes 



