DIAGNOSIS: Body short, dorsoventrally flattened. Prostomium with three 

 antennae. Two pairs of tentacular cirri. Antennae, tentacular, and 

 dorsal cirri globular. Dorsum without large, globular tubercles. Phar- 

 ynx with middorsal tooth and trepan. 



Plakosyllis quadrioculata Perkins, 1931 

 Figures 30-95, 96a-e 



Plakosyllis quadrioculata Perkins, 1981:1108, figs, lla-f, 12a-i. 



MATERIAL EXAMINED: 

 Gulf of Mexico BLM-OCS: 



SOFLA 2D-11/80 (2 spec, USNM 75298); MAFLA 2315A-8/76 (2 spec), 2423J- 

 7/75 (2 spec, USNM 65685), 2423-11/77 (1 spec), 2530D-6/75 (2 spec), 

 2853D-9/77 (1 spec); STOCS HRl-5 F/76 (1 spec, USNM 75221), HR1-2 

 11/76 (1 epitoke, USNM 75220). 

 Supplementary Material: 



Florida — Hutchinson Island, St. Lucie County, T. Perkins ID., 11.8 m 

 (USNM 60219, holotype). 

 DESCRIPTION: 



Length, to 1.9 mm (previously reported to 3.0 mm); width, to 0.5 mm 

 (previously reported to 0.3 mm). Body small, flattened; complete speci- 

 mens with up to 54 setigers. Prostomium rectangular, wider than long, 

 lobed anteriorly (Figure 30-96a), with four small, lentigerous eyes, two 

 dorsal and two ventral. Antennae globular; median antenna arising from 

 anterior margin of prostomium, lateral antennae arising anteroventrally. 

 Palps ventral, globular, contiguous. Nuchal organs as ventrolateral 

 ridges between prostomium and peristoraium, not visible dorsally. Dorsal 

 tentacular cirri arising on extensions of peristomium lateral to eyes; 

 ventral tentacular cirri smaller, not visible dorsally. Dorsal cirri 

 globular, situated on stout cirrophores. Ventral cirri auricular, ex- 

 tending beyond parapodia. Anal cirri paired, globular. Dorsum smooth, 

 or with segmental ridges, or with longitudinal rows of low rounded 

 tubercles or internal gland-like structures. Superior composite falci- 

 gers numbering 2-4 per fascicle, with short, serrate, unidentate blades 

 and serrate shaft-heads (Figure 30-96b). Inferior composite falcigers 

 with smooth blades (Figure 30-96c); shaft-heads smooth or with few 

 coarse serrations. Inferior simple seta slender, falcate, sharply 

 pointed (Figure 30-96d). Superior simple seta absent. Acicula stout 

 and emergent in all parapodia (Figure 30-96e). Pharynx extending to 

 setigers 4-7. Proventricle extending from setigers 5-7 to 6-9, with 13 

 (11-15) muscle cell rows. Epitoke with four large, lentigerous eyes, 

 two dorsal and two ventral on two small anterior lobes; prostomial 

 appendages, pharynx and proventricle absent; bidy cavity filled with 

 gametes. Differentiation into sexual stolon beginning on setiger 31 of 

 holotype. 



REMARKS: Perkins (1981:1111) described the pharyngeal margin of _P. 

 quadrioculata as having a trepan of ten small teeth in addition to a 

 middorsal tooth. These structures could not be seen in Gulf of Mexico 

 BLM-OCS specimens owing to their small size. T ^rkins also noted a close 

 alliance between Plakosyllis and Trypanosyllis , and suggested that both 

 Plakosyllis and the closely related Eurysyllis be referred to the Syl- 

 linae. That suggestion has been followed herein. P. quadrioculata is 

 newly reported from the Gulf of Mexico. 



30-101 



