REMARKS: Opisthodonta sp. B from Gulf of Mexico BLM-OCS collections, 

 from North Carolina, and from the east coast of Florida has been con- 

 fused with Pionosyllis uraga Imajima, 1966, from Japan. It differs from 

 the latter in having the middorsal pharyngeal tooth located medially, 

 rather than anteriorly; in having auricular ventral cirri extending well 

 beyond the anterior parapodia; and in having the cutting margin of the 

 falciger blades surrounded by a semi-transparent hood. Opisthodonta sp. 

 B differs from 0. pterochaeta Southern, 1914, in having long-bladed, 

 spiniger-like setae anteriorly; in having the short-bladed falcigers 

 with a distinctly larger subterminal tooth; and in having fewer proven- 

 tricular muscle cell rows. 



PREVIOUSLY REPORTED HABITAT: 11-130 m; coarse calcareous sand. 

 GULF OF MEXICO BLM-OCS OCCURRENCE: Common in northeastern Gulf (Figure 

 30-57); 10-189 m; coarse to fine sand, silty fine to very fine sand, 

 clayey silt, clayey sandy silt. 

 DISTRIBUTION: North Carolina, Florida, Gulf of Mexico. 



Genus Pionosyllis Malmgren, 1867 



TYPE SPECIES: Pionosyllis compacta Malmgren, 1867b. 

 REFERENCES : 

 Imajima, 1966:114. 

 Day, 1967:261. 

 Fauchald, 1977a:83. 



DIAGNOSIS: Prostomium with three antennae; palps basally fused or 

 separate. Nuchal organs often as distinct ciliated ridges along poste- 

 rior border of prostomium. Two pairs of tentacular cirri. Antennae, 

 tentacular and dorsal cirri smooth or weakly articled. Pharynx armed 

 with single tooth; anterior margin smooth. 



Key to the Gulf of Mexico BLM-OCS Species of Pionosyllis 



la. Dorsal cirri shorter than body width 2 



lb. Dorsal cirri longer than body width or alternating long and short 

 3 



2a. Composite falcigers with homogomph shaft-heads and distinctly 

 bidentate blades (Figure 30-60c,d); acicula small, slender, not 

 emergent Pionosyllis weismanni, p. 30-67 



2b. Composite falcigers with heterogomph shaft-heads and unidentate to 

 minutely bidentate blades (Figure 30-62b,c); acicula large, thick, 

 emergent (Figure 30-62f) Pionosyllis sp. B, p. 30-69 



3a. Blades of all composite setae similar in length (Figure 30-64c,d); 



dorsal cirri alternating long and short (Figure 30-64a) 



Pionosyllis gesae, p. 30-69 



3b. Blades of superior composite setae at least twice as long as 



blades of inferior composite setae (Figure 30-66d,e); all dorsal 



cirri long (Figure 30-66a) 4 



4a. Eyes absent; nuchal organs small (Figure 30-66a); body slender, up 

 to 0.6 mm wide including parapodia. . .Pionosyllis sp. A, p. 30-72 



30-65 



