310 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 15 



Family Characteristics 



Most members of Paraonidae are small to very small, threadlike 

 forms; the largest measure about 40 mm long and most are between 10 

 and 20 mm long and small species are 8 mm long or less. Segments are 

 numerous, indefinite in number, and range to 150 (Hartman, 1944d, 

 pp. 314-317). Their resemblance to the Orbiniidae and Apistobranchidae 

 is emphasized by the presence of dorsally directed, laterally fimbriated 

 branchiae. In the Paraonidae, however, the branchiae are not present 

 before the fourth or fifth segment and are absent from a long to short 

 posterior end of the body. In the Apistobranchidae the branchiae are 

 present from the first parapodium and in the Orbiniidae the branchiae 

 are present to the end of the body. Resemblance to the Spionidae is sug- 

 gested by the shape of the prostomium and by the hooded neuropodial 

 uncini. In Cirrophorus resemblance to some Cirratulidae is noted in the 

 presence of heavy acicular spines in some parapodia. 



The body consists of a prostomium that is clearly visible, a pre- 

 branchial region of three to many segments, a branchial region of 8 to 

 60 or more segments, and a long postbranchial region. The anal end or 

 pygidium usually has a pair of lateral and a midventral process. The 

 prostomium is semicircular to depressed conical or truncate in front ; in 

 some species it narrows posteriorly, in others it widens. Paired eyespots 

 are present at the sides or they are absent. A pair of nuchal organs 

 resembling semicircular slits is sometimes conspicuous at the sides of the 

 prostomium. A median antenna is present {Aricidea) or absent (Para- 

 onis) ; it is simple and cirriform or long to short, or clavate to short and 

 papillar; it is rarely branched in its terminal part. 



The proboscis is an eversible epithelial pouch, not known to be 

 branched or lobed. The first or second visible segment has biramous 

 parapodia provided with setae. In the prebranchial region both rami 

 have long slender capillary setae. The notopodial postsetal lobe (called 

 also dorsal cirrus) may be prolonged and triangular or cirriform or in- 

 conspicuous. The corresponding neuropodial lobe (called also ventral 

 cirrus) may be similar but is broader at the base and shorter or absent. 



The branchial region is usually wider than the rest of the body and 

 sometimes broadly depressed ; its parapodia are larger and its setae 

 stronger and more numerous than those in other segments. Notopodia 

 have distally pointed setae sometimes accompanied by furcate (lyre) 

 setae ; its postsetal lobes may be long and cirriform to foliose or divided. 



