190 



Fam. 12. Oncaeidae. 



General Characters. Body of rather different shape in the different 

 genera, but with the anterior and posterior divisions always well defined, the 

 latter generally rather slender and attenuated. Eye imperfectly developed or 

 quite absent. Anterior antennae not much elongated, with the number of joints 

 more or less reduced. Posterior antennae imperfectly prehensile. Maxillae and 

 anterior maxillipeds comparatively small. Posterior maxillipeds, as a rule, 

 powerfully developed in both sexes, terminating in a clawed hand. Natatory 

 legs with both rami 3-articulate, the inner one generally more slender than 

 the outer. Last pair of legs small, uniarticulate. 



Remarks. This family was originally established by Giesbrecht to 

 comprise 5 different genera, viz., O/iccea, Concea, Lubbockia, Pachysoma and 

 Ratania. The last named genus was however subsequently removed by that 

 author and referred to the siphonostomous Cyclopoida (Asterocheridae). A 

 new genus referable to the present family, Pseiidolubbockia, has more recently 

 been added by the present author, so that the family still comprises 5 genera. 

 The most aberrant of these genera is unquestionably the genus Pachysoma 

 of Glaus, the systematic position of which seems to me to be rather question- 

 able. All the forms comprised within the present family lead a true pelagic 

 existence; but it is very probable that, like the Lichomolgidce, they are in 

 reality semiparasitic in habits, though it has not yet been stated which pelagic 

 animals are at time infested by them. Of the above-named genera only one 

 is as yet represented in the Fauna of Norway. 



Gen. 46. Oncsa, Philippi, 1843. 



Syn: Antaria, Dana. 



Generic Characters. 'Body cyclopoid in shape, with the anterior division 

 more or less dilated and strongly vaulted above. Cephalon distinctly defined 

 from the 1st trunkal segment, and having below the front an obtuse incurved 

 rostral prominence. The 3 succeeding segments gradually diminishing in size, 

 and having the epimeral parts rounded and but little prominent. Last trunkal 

 segment very small, though distinctly defined. Tail attenuated and composed 

 in female of 4, in male of 5 segments, the 1st of which (the genital segment) 



