CYCLOPOIDEA. ^Q4Q 



the first of the longer setae), is shorter than the second, which is 

 always the longest seta of the stylets. 



The position of the antennae, mouth, and organs about the mouth, 

 and immediately posterior to it, are shown on Plate 75. The buccal 

 mass (m) is quite large, and has behind a ciliated lip. The nerves to 

 the anterior antennae are also shown. 



A young individual, probably of a Calanus, is represented in figure 

 3, Plate 76. Length, one-thirtieth of an inch. There are three 

 pairs of jointed organs ; the first simple, and the other two, two- 

 branched, each branch one-jointed. It was collected, in the harbour 

 of Rio Janeiro, January, 1838. 



The Calani are among the most common of the oceanic Cyclopoidea. 

 Their colours are either a faint tinge of red, purple, or bluish purple, 

 rarely a pure blue, like many Pontellae. 



The genus Calanus was instituted and incorrectly characterized by 

 Leach. As the species here described are evidently congeneric with 

 the Calanus finmarchianus (Leach), we adopt the generic name, with- 

 out his generic description. The genus Temora of Baird, was insti- 

 tuted in 1850 (Brit. Entomost., p. 227), for the Calanus finmarchianus 

 of Leach, and, therefore, upon the same type as that of Leach's genus. 



I. Set^i antennarum Imarum apicales subapicalibus longiores. 

 a. Styli caudales vix ohlongi. 



Calanus rotundatus. 



Frons rotundatus. Ceplialothorax 4:-articulatus y crassus, posticd obtusus. 

 Antennae, antico3 corpore vix breviores, 24c-articulata3, duplo curvatw, 

 apicibus fronte paulo posterioribus, articulo ultimo elongato; setis apica- 

 libus articulum idtimum longitudine wquantibus, anticis wpice remotis, 

 setis sub-apicalibus minutis. Styli caudales brevissimi; setis inosquis, 

 secundis abdomine longioribus et apice divaricatis. 



Front rounded. Cephalothorax four-jointed, stout, obtuse behind. 

 Anterior antennae about as long as body, twenty-four-jointed, doubly 

 curved, apices behind line of beak, apical joint elongate ; apical setae 



263 



