Fam. 1 . Oithonidae. 



Characters. Body slender and of a very delicate structure, with thin 

 and pellucid integuments. Anterior antennae in female very slender and provided 

 with long diverging setae; those in male much more robust and distinctly geni- 

 culate. Posterior antennae comparatively small, with the number of joints reduced. 

 Oral parts well developed, and rather different in structure from those in other 

 Cyclopoida, being partly armed with claw-like spines. Natatory legs with com- 

 paratively slender 3-articulate rarni edged with unusually long setae. Last pair 

 of legs rudimentary and partly confluent with the corresponding segment. Caudal 

 rami differing in shape and armature in the two sexes. 



Remarks. This family is founded upon the genus Oiihona Baird, which 

 in several respects differs rather conspicuously from the other genera included 

 in the present section, and may accordingly be entitled to constitute the type 

 of a distinct group. We do not know as yet any other genus referable to this 

 family. The genus Mormonilla of Giesbrecht, it is true, exhibits some resemblance 

 to Oithona in the general appearance of the body as also in the structure of 

 the anterior antennae; but the posterior antennae are very different and built 

 wholly on the type of the Calanoida. The systematic position of this genus is 

 still very doubtful, though it perhaps may be found to be nearest related to the 

 Cyclopoida. In this case it must be regarded as the type of a very anomalous 

 family of the gnathostomous Cyclopoida. 



Gen. 1. OlthOna, Baird, 1843. 



Syn : Scribella, Dana. 



Generic Characters. Body slender and attenuated, with the anterior 

 division only slightly dilated, the posterior very narrow, linear in form. Head 

 defined from the 1st pedigerous segment by a well-marked suture, and generally 

 produced in front to a sharply-pointed rostrum, wanting, however, in male. 

 Anterior antennae long and slender, scarcely tapered distally, and composed of a 

 limited number of joints, some of which are imperfectly defined. Posterior an- 

 tennae abruptly bent in the middle, and apparently only consisting of 2 joints, 

 the 1st carrying about in the middle behind a short seta arising from a knob- 

 like prominence. Mandibular palp with the basal part greatly produced, pediform, 

 terminating in 2 claw-like spines, inner ramus represented by a very small seti- 



