328 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



tentacles continue to be conspicuous through planktonic existence and into 

 the adult in most species ; they are the precursors of the paired palpi, 

 conspicuous in some (Phalacrostemtna and Lygdamis), but more or less 

 concealed by the oral tentacles in others (Fhragmatopoma) . A pair of 

 small tentacular structures, near the palpi and also ventral in position, 

 are believed to be the rudiments of the oral tentacles. When fully devel- 

 oped, in the sedentaiy adult, they may be very numerous, in ranks of 7 to 

 11 rows, at the sides of the oral aperture. In Phalacrosteinma (p. 330) 

 they are absent, but the palpi are correspondingly enlarged and take over 

 the function (food intake) of the oral tentacles in other species. 



The 2 anterior, thoracic segments are slow in making their appear- 

 ance; they arise just behind, and below, the great setal sacks. The first 

 of these is believed to be only the neuropodial portion of the segment 

 immediately preceding; the second is biramous. The large, glandular, 

 U-shaped area just behind the mouth is the so-called building organ 

 (Wilson, 1929) which secretes mucus for the adhesion of sand particles 

 in tube construction. From the third segment the parapodial paleae are 

 more or less conspicuously developed, even in very young stages. Inversion 

 of parapodia, marking the transition from thorax to abdomen, is marked 

 already in pelagic stages. The caudal tail is represented only by a thick, 

 glandular area (pi. 29, fig. 17), and comes to assume its attenuate form 

 only after settling. 



Systematic. — The Sabellariidae are generally recognized through 7 

 genera (Johansson, 1927, p. 81) mclwding Phalacrostermna Marenzeller, 

 Lygdamis Kinberg, Cryptopomatiis Gravier, Idanthyrsus Kinberg, Gun- 

 nerea Johansson, Fhragmatopoma Kinberg, and Sabellaria Lamarck. Two 

 others, Eupallasia Augener (1927, p. 236) and Monorchos Treadwell 

 ( 1926, p. 191 ) are referred to the older Lygdamis (p. 331 ). In addition, 

 Tetreres Caullery has long been considered identical with Lygdamis 

 (Johansson, 1927, p. 81 ) and the following referred to Sabellaria, includ- 

 ing Centrocorone Grube, Chrysodon Oken, and Hermella Savigny 

 (Fauvel, 1927, p. 206). 



Representatives from the Western Hemisphere belong to 4 genera, 

 including Idanthyrsus Kinberg^, Lygdamis Kinberg, Fhragmatopoma 

 Morch, and Sabellaria Lamarck. These 7 genera are separable as follows. 



1 Fauvel (1927, p. 213) uses Pallasia Quatrefages to include both Idanthyrsus 

 Kinberg and Lygdamis. Since Pallasia Quatrefages (1866) is preoccupied in groups 

 of insects and fishes (Annenkova, 1925, p. 125), Idanthyrsus is the next available. 

 I consider Lygdamis distinct from the first, as indicated in the key below. 



