498 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



entire . A. rigida 



4. Posterior dorsal hooks recurved distally (pi. 61, fig. 6) ; cirri 

 articulated A. cingulata 



5. Fourth segment forms a constricted neck region .... 



. A. constricta 



5. Fourth segment does not form such a neck region ... 6 



6. Posterior margin of prostomium deeply excavate for insertion of 

 median antenna; large dorsal hooks already present from the 

 fourth setigerous segment . . . . .A. tentaculata 



6. Posterior margin of prostomium not so excavate; large dorsal 

 hooks first present from a more posterior segment ... 7 



7. Dorsal acicular hooks brown, first present at about the sixty-ninth 

 segment; proboscis terminates distally in 16 papillae . 



. A. robusta 

 7. Dorsal acicular hooks yellow, first present at about the twenty- 

 fifth segment; proboscis terminates distally in 14 papillae . 

 A. bassi 



Ancistrosyllis rigida Fauvel 

 Plate 62, Figs. 1-7 



Fauvel, 1919, p. 373, fig. 4; 1919, pp. 210-211. 



Kynephorus inermis Ehlers, 1920, p. 27, pi. 3, figs. 1-9. 



Fauvel, 1923, pp. 18-19, fig. 3. 



Augener, 1927, p. 134. 



Fauvel, 1932, p. 64. 



A. gorgonensis Monro, 1933, pp. 26-28, fig. 12. 



Collections. — El Descanso, Lower California, shore ( 1 ) ; La Jolla, 

 California, shore (2). 



The largest complete individual measures 21 mm long and 1 mm 

 wide ; it consists of 84 segments. The body is slender, smooth, rigid, and 

 resembles a wiry syllid. Epithelial papillae appear to be entirely lacking 

 except for the unique pair at the outer bases of the palpostyles (pi. 62, 

 fig. 1). 



The prostomium consists of a pair of lateral lobes that are separated 

 from each other by a triangular middle lobe. Paired, fusiform antennae 

 are inserted at the distal margins of the lateral lobes and a similar, median 

 antenna is inserted at the posterior middle margin of the median lobe. A 

 single pair of dark eyes is located on the paired lobes, near their posterior 

 margin. These 2 eyes are proportionately larger than are the 4 eyes 



