CYCLOPOIDEA. 1069 



The front forms a low obtuse angle between the antennae. The 

 cephalothorax narrows posteriorly, and the last segment is about twice 

 the breadth of the first abdominal. The last joint of the antennae is 

 longer than the preceding. The posterior subapical setae are about 

 twice as long as the last two joints ; the anterior and posterior prae- 

 antepenult are very short; the apical are short, two extending back- 

 ward, and one or two obliquely outward and forward. 



Calanus tenuicornis. 



Frons rotundatus. Cephalothorax h-articulatus, postich obtusus, segmentis 

 4 posticis subcequis. Antennce anticce sesqui corporis longitudine, tenuis- 

 simce, duplo levissime curvatce, apicibus fronte vix poster ioribus, articulis 

 tribu8 ultimis subcequis; setis brevibus, articidi tertii setd longiore, 

 setis cluabus posticis subapicalibus prcelcmgis, anticd pemdtimd fere 

 dimidio t breviore, apicalibus brevibus. Styli caudales oblongi (Jatitu- 

 dine duplo longiores). 



Front rounded. Cephalothorax five-jointed, posterior angles a little 

 elongate, but obtuse, the last four segments nearly equal. Anterior 

 antennae nearly one and a half times as long as body, very slender, 

 slightly doubly curved, tips nearly in line of front, last three joints 

 subequal, setae short, one a little longish on the third joint, two sub- 

 apical, posterior quite long, anterior penult more than half shorter, 

 apical short. Caudal stylets twice as long as broad. 



Plate 73, fig. 10 a, animal, enlarged ; b, extremity of antenna. 



Taken, July 2, 1841, in the Pacific, latitude 40° north, longitude 

 157° west. 



Length, one-twelfth of an inch. Nearly colourless. The posterior 

 antepenult seta of the anterior antennae is as long as last six or seven 

 joints of the antennae; the penult is a fourth shorter; the apical are 

 shorter than the joint. At apex of seventh joint from the extremity 

 there is a prominent seta, nearly as long as two joints of the antenna, 

 and equalling the seta from the third joint. The caudal setae were 

 broken off in the specimen examined. The posterior antennae have 



268 



