362 THE ANNELIDA POLYCHAETA. 



Since Levinsenia Mesnil (1897) has been shown by Cerruti (Mitth. Zool. sta. 

 Neapel, 1909, 19, p. 459-512, pi. 18, 19) to be a synonym of Paraonis Grube 

 (1873), the family name is by that author properly changed to Paraonidae. A 

 conspicuous structural difference between Ariciidae and Paraonidae lies in the 

 complete lack of cross-ridged, or camerated, setae in the latter. All have a slight 

 sensory papilla at the apex of the prostomium and may or may not have also a 

 tentacle. Aricidiopsis Johnson is synonymous with Aricidia Webster. 



Key to Genera. 



a. With no tentacle. 



6. With specially modified stouter setae or spines, often as hooded crochets, occurring only in the 



posterior neuropodia Paraonis Grube. 



bb. Such modified setae occurring only in the posterior notopodia Paraonides Cerruti. 



aa. A tentacle present, dorsal in position. 



b. Specially modified stout setae or spines occurring only in the posterior neuropodia. 



Aricidia Webster. 

 bb. Such setae occurring only in the posterior notopodia, these setae acicular in character. 



Cirrophorus Ehlers. 



GONIADIDAE. 



These are forms of medium or large size in which the body is elongate, 

 slender, and somewhat depressed, and is composed of numerous somites. Colors 

 normally weak and uniform; sometimes pinkish from the blood, v/hich, as in the 

 Glyceridae, contains large corpuscles in which haemoglobin is present; some show 

 a different color, such as a greenish tinge, when carrying ripe ova. 



The prostomium slenderly conical and divided into from seven to eleven 

 annuli, of which the most anterior bears four small tentacles. Eyes either present 

 or absent. 



Nephridia with inner end closed and with solenocytes. A genital funnel 

 opening into nephridial duct at time of ripening of sex products. 



Parapodia of anterior region of the body uniramous, those of the middle 

 and posterior regions biramous. Neurocirri conical. Notocirri more or less 

 flattened. 



Setae of the uniramous parapodia simple. In the biramous parapodia 

 the notopodial setae are simple, the neuropodial composite. 



Anal cirri two. 



The proboscis is long. As in the Glyceridae it bears at its distal end a 

 circle of normally eighteen pai)illae, of which one lies in the middorsal and one 

 in the midventral line. The chitinous pieces of the armature are numerous, 

 consisting of few, large hooks, or toothed jaws proper, and more numerous, smaller 



