difficult to describe either qualitatively or morphometrically. Inves- 

 tigators attempting to identify individuals belonging to this subgenus 

 are urged to use phase contrast or differential interference contrast 

 microscopy and high magnification immersion objectives to examine setal 

 structures. The use of a good clearing medium-such as Hoyer's will 

 enhance the visibility of internal structures. 



Key to the Gulf of Mexico BLM-OCS Species of Syllis ( Typosyllis ) 



la. All or some composite falcigers unidentate to subbidentate. . . 2 

 lb. All composite falcigers bidentate or bifid 3 



2a. All falcigers unidentate or subbidentate (Figure 30-120b-d). . . . 



Syllis (Typosyllis) arnica, p. 30-127 



2b. Falcigers of anterior and posterior regions bidentate; falcigers 



of tnidbody region unidentate or subbidentate (Figure 30-122d,e). . 



Syllis (Typosyllis) armillaris, p. 30-129 



3a. Falcigers unequally bifid (Figure 30-124b-d) 



Syllis (Typosyllis) sp. G, p. 30-131 



3b. Falcigers bidentate (Figure 30-128b-e) 4 



4a. Blades of inferior falcigers from medial to posterior regions with 

 terminal or subterminal tooth enlarged (Figures 30-126e, 128e) 

 relative to teeth of superior falcigers 5 



4b. Blades of inferior falcigers from medial and posterior regions 

 with terminal and subterminal teeth not enlarged relative to teeth 

 of superior falcigers 6 



5a. Blades of inferior falcigers from medial and posterior regions 

 enlarged, with terminal and subterminal teeth unequal in size and 



perpendicular to each other (Figure 30-126e) 



Syllis (Typosyllis) sp. A, p. 30-134 



5b. Blades of inferior falcigers from medial and posterior regions not 

 enlarged, with terminal and subterminal teeth equal in size and 



parallel to each other (Figure 30-128e) 



Syllis (Typosyllis) sp. C, p. 30-134 



6a. Superior composite falcigers of midbody region with terminal tooth 

 minute and knob-like (Figure 30-130b); blade-length ratio 2.2-5:1 



• Syllis (Typosyllis) cf. lutea, p. 30-136 



6b. Superior composite falcigers of midbody region with terminal tooth 

 not minute and knob-like; blade-length ratio less than 2.2:1. . 7 



7a. Blades of superior composite falcigers from anterior region with 

 indistinct terminal and subterminal teeth (Figure 30-132b) . . . . 

 Syllis (Typosyllis) sp. F, p. 30-139 



7b. Blades of superior composite falcigers from anterior region with 

 distinct terminal and subterminal teeth (Figure 30-134b). ... 8 



8a. Proventricle less than twice as long as wide; dorsal cirri long 



(Figure 30-134a) Syllis (Typosyllis) sp. D, p. 30-139 



Proventricle more than twice as long as wide; dorsal cirri long or 

 short 9 



30-125 



