Clare Island Survey — Archiannelida and Pohjchaeta. 47 63 



lost their connexion with the head, and are directly seated on the brain, in a 

 very backward position. Secondly, the dorsal cirrus of the second setigerous 

 segment, which in Pisione is elongate and functions as a tentacular cirrus, in 

 the Irish species is unmodified. Thirdly, the genital papillae, so prominent in 

 the posterior segments of Pisione, are absent in the Irish specimens. 

 The provisional diagnosis of the new genus would be as follows : — 



Praegeria 1 gen. nov. 



Pisionidae ivith greatly reduced head ; ventral cirrus of first setigerous 

 segment elongate, and functioning as a tentacular cirrus ; dorsal cirrus of second 

 setigerous segment globular, as on the following segments ; genital poipillae 

 absent ; anterior parapodia with one, posterior para/podia ivith tv;o simple setae. 



The geographically isolated position of this form is indicated by the 

 specific name remota. Ehlers expressed the opinion that the simple setae in 

 the feet of Pisione might be only compound setae which had accidentally lost 

 the terminal pieces, but the spinous structure of the bevelled tip in Praegeria 

 shows that they are true simple setae. This is confirmed by the smooth 

 tapering tip of the simple seta which appears in the posterior feet, and which 

 differs widely from the shaft of the compound setae. 



As regards the affinities of the Pisionidae, I agree with Ehlers in the 

 opinion that they approach most nearly to the Aphroditidae. They resemble 

 the sub-family Sigalioninae in the reduction of the head and its appendages, 

 the forward position of the buccal segment, the shape of the compound setae, 

 and the presence of jaws. I am of the opinion that the elongate ventral 

 anterior cirri of the Pisionidae are homologous to the palps of the Sigalioninae, 

 that the slender dorsal and globular median cirri, together with the swollen 

 bases which contain the prominent spines, constitute the parapodia and cirri 

 of the buccal segment, the whole being homologous to the segment bearing 

 tentacular cirri in Pholoe, and the first setigerous segment in Sthenelais. The 

 first setigerous segment in the Pisionidae would then be homologous to the 

 first setigerous segment in Pholoe and to the second in Sthenelais. In all 

 three cases the ventral cirrus of this segment is elongate and functions as 

 a tentacular cirrus, a remarkable resemblance, which is best explained by the 

 theory of close relationship. In the Pisionidae, the foot has been greatly 

 reduced, and the former existence of the dorsal division is only witnessed by 

 the presence of a single spine. The compound setae, however, closely 

 resemble those of Pholoe. The affinities with the families Nephthydidae, 

 Hesionidae, and Syllidae, which Ehlers discusses, seem to be far more 

 problematical and dubious. 



1 This genus is named after R. Lloyd Praeger, to whom are due the initiation and organization of 

 the Clare Island Survey. 



