117 



Fam. 17. Heterorhabdidae. 



Characters. Body more or less depressed, and generally highly pellucid 

 Cephalosome well defined from the 1st pedigerous -segment, front more or less 

 produced, and carrying below 2 delicate tentacular filaments. Last 2 segments 

 of metasome united. Urosome consisting in female of 3 or 4 segments, in male 

 of 5 segments. Caudal rami of different shape in the different genera, in some 

 cases asymmetrical; setse present in the normal number. Anterior antennae very 

 slender, in some cases of quite an extraordinary length, and composed in female 

 of 25 articulations ; left antenna in male generally geniculate. Posterior antennae 

 with the rami more or less unequally developed. Oral parts, especially mandibles 

 and maxillse, differing conspicuously in their structure from those parts in other 

 Calanoids. Legs with both rami triarticulate ; last pair biramous and natatory, 

 like the preceding pairs, outer rami of this pair slightly transformed in male. 

 No ovisac present in female. 



Remarks. The forms belonging to this family, in the restriction here 

 adopted, are chiefly characterised by the pellucid, more or less depressed body, 

 the very slender anterior antenna?, the anomalous structure of some of the oral 

 parts, and finally, by the fact that the last pair of legs are biramous and nata- 

 tory, like the preceding pairs. In the last-named character, this family agrees 

 with the CentropcCgidce ; but it is otherwise very different. The family comprises 

 at present 3 distinct genera, viz., Heterorhabdus, Giesbr., Haloptilus, (iriesbr. and 

 Augaptilus, Giesbr. The first 2 of these genera are represented in the fauna 

 of Norway, and will by treated of below. 



Gen. 20. HeterOrhabdUS, Giesbrecht, 1898. 



Syn: Hcterochceta, Claus (not Westwood). 



Generic Characters. Body more or less robust, with the anterior division 

 somewhat vaulted above, and depressed only in its anterior part. Cephalosome 

 comparatively short, with a well-marked cervical depression above in the middle, 

 front slightly projecting in front and carrying below 2 nearly straight tentacular 

 appendages. Lateral parts of last segment of metasome not produced. Urosome 

 of moderate length, and consisting in female of 4 segments, the last of which, 

 however, is imperfectly defined from the caudal rami; the latter scarcely at all 



