Fam. 1. Calanidae. 



Characters. Cephalosome well defined, or coalescent with the 1st pecliger- 

 ous segment; front carrying below 2 soft posteriorly curving tentacular filaments. 

 Last pedigerous segment not confluent with the preceding one, and having the 

 lateral corners but slightly produced. Urosome not very slender, consisting in 

 female of 4, in male of 5 segments, caudal rami comparatively short, with the 

 normal number of setae. Eye simple, very small, subventral. Anterior antennae 

 in female long and slender, consisting of 25 articulations, which are supplied 

 anteriorly with comparatively short and uniform bristles; penultimate and ante- 

 penultimate articulations each having behind an unusually strong and densely 

 plumous seta extended straight backwards. Anterior antennae in male thickened 

 at the base, with some of the proximal articulations fused together and supplied 

 below with a restricted number of comparatively short sensory appendages. 

 Posterior antennae with the rami of about equal length. Oral parts of normal 

 structure, being but slightly transformed in male. Legs with both rami 3-articulate, 

 terminal joint of outer ramus with only 2 spines outside. 5th pair of legs in 

 female of a similar structure to that in the preceding pairs, in male more or 

 less transformed, left leg the stronger. 



Remarlcs. This family, answering to the subfamily Calanince of Dr. 

 Giesbrecht, is chiefly characterised by the structure of the 5th pair of legs, 

 which, at any rate in the female, are natatory and of a similar appearance to that 

 of the proceeding pairs. Moreover, the long and slender anterior antennae, with 

 the 2 remarkably developed subapical setae, furnish an easily recognizable character. 

 The family comprises as yet only 2 genera, viz., Calanus Leach, and Undina 

 Dana. These 2 genera, it is true, have been combined by Dr. Giesbrecht; but 

 I think that they ought more properly to be kept apart, as the structure of the 

 last pair of legs in the male differs conspicuously in the 2 genera. In the 

 northern seas only the first-named genus is represented. 



Gren. 1. CalanUS, Leach, 1816. 



Syn: Cetochilus, Roussel de Vauz^me, Baird, Glaus. 



Generic Characters. Body comparatively slender, with the anterior divi- 

 sion oblong subcylindric in form, and more than twice as long as the posterior. 



