CYCLOPOIDEA. 1097 



Genus OITHONA, Baird. 



Antennce anticce elongatce, articulis paucis, prcelongis, setis diffusis, longis. 

 Antennas posticce simplices (?) . Maxillipedes ad articulationem secundum 

 geniadati, prorsus projecti, setis spinulosis validis instructi. Abdo- 

 men lineare, corporis longitudine. Styli caudales oblongi, divaricati, 

 setis prcelongis. jScepius e basi pedum biremium seta grandis scepe 

 plumiformis lateraliter porrecta. 



Anterior antennae long; joints few but long, setae pointed different 

 ways and quite long. Posterior antennae simple (?). Maxillipeds 

 geniculate between the first and second joints, and thrown forward, 

 furnished with long spinulous setae. Abdomen as long as the body. 

 Caudal stylets oblong, divaricate, setae very long. Usually a long 

 seta, often plumiform, projecting laterally from the base of the 

 natatory legs. 



The Oithonae have a long slender abdomen, and are not over one- 

 twentieth of an inch in their whole length. They are like a minute hair 

 in the water, scarcely visible to the naked eye, because proportionally 

 so narrow; under a microscope, they are remarkable for their spread- 

 ing antennae, with long diffuse setae, the long divaricate setae of the 

 caudal stylets, and the plumes or coloured setae along the sides of 

 the body. 



The anterior antenna? are about as long as the body, and have not 

 far from seven unequal joints. Many of the setae are more than half 

 as long as the organ. 



The posterior antennas are three-jointed. The third oblong, and 

 bearing at apex two long stout setae, besides one or two shorter. The 

 second is much shorter than the third, and also bears some setae. 



The mandible has a slender denticulate summit. The basal part 

 projects at right angles with the mandible into an oblong process, 

 having at apex two remotely spinulous setae. The palpus is one- 

 jointed, and has one or two naked setae at apex. 



The maxilla consists at its inner extremity of four stout digitiform 

 or spiniform processes, which extend inward, nearly parallel and a 

 little distant from one another. From this part, at right angles with 

 it, there is an oblong process (like that of the mandible), having one 



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