CALANUS. 37 



Sub-family 1. CALANINJI, Dana. 



This sub-family is characterised by the presence of 

 only one eye which is made up of several lenses ; by 

 the 2i 25-jointed anterior antennae and by the long 

 and slender form of both thorax and abdomen : rostrum 

 slender, and usually, if not always, furcate. 



Genus 1. CALANUS, Leach (1819). 



(LEACH, Diet. Sc. Nat., xiv, Art. Entomostraca.) 

 (Cetochilus, Roussel de Vauzeme, Glaus, Baird.) 



Cephalothorax elongated, slender, consisting of five 

 segments. Head produced into an attenuated, forked 

 rostrum. Eyes small, situated at the back of the 

 head, near the middle line, and composed each of two 

 lenses. Anterior antennae very long, composed of 

 twenty-five joints ; alike on the right and left sides in 

 both sexes, and possessing no hinge-joint: those 

 of the male are provided with thickened, club- 

 shaped hairs. Posterior antennae two-branched, the 

 secondary branch having four small intercalated 

 median joints. Maxilla forming a broad laciniated 

 plate, armed with strong marginal setae, some of 

 which are plumose, and having attached to it two 

 short and broad leaflike processes, which bear long 

 branchial filaments. Mandibles large and strong, the 

 cutting portion ending in a wide sharply- toothed mar- 



