Exogone lourei — Banse arid Hobson, 1974:58, fig. 14h-j. 

 Exogone lourei — Perkins, 1981:1092. 



MATERIAL EXAMINED: 

 Gulf of Mexico BLM-OCS: 



SOFLA 22-11/80 (2 spec, USNM 75288), 28-11/80 (5 spec, USNM 75289), 

 28B-11/80 (1 spec, USNM 75290); MAFLA 2211C-7/76 (1 spec), 2211E-7/76 

 (3 spec), 23161-11/77 (3 spec), 24241-7/76 (3 spec), 2529A-11/77 (2 

 spec, USNM 55821), 2534G-6/75 (1 spec), 2644A-6/75 (1 spec). 

 Supplementary Material: 



3ritish Columbia — False Narrows, May 1936, E. and C. Berkeley coll./ID. 

 (USNM 32895, holotype). 

 DESCRIPTION: 



Length, to 8.0 mm (previously reported to 8 mm); width, 0.2 mm. Body 

 small, thread-like; complete specimens with up to 52 setigers. Pro- 

 stomium pentagonal, with four small to large lentigerous eyes in trape- 

 zoidal arrangement. Median antenna fusiform, about as long as palps; 

 lateral antennae ovoid, small (Figure 30-34a). Palps long, completely 

 fused dorsally. Nuchal organs as inconspicuous lobes at postectal 

 corners of prostomium. Tentacular, dorsal and ventral cirri ovoid. 

 Dorsal cirri present on all setigers. Superior simple seta blunt, 

 minutely serrate, present from setiger 1, sharply bent posteriorly 

 (Figure 30-34b). Composite spinigers (Figure 30-34c) numbering 1-2 per 

 fascicle; those of setiger 2 having greatly enlarged shaft-heads (Figure 

 30-34d). Composite falcigers bidentate with minute terminal tooth (Fig- 

 ure 30-34e,e'). Inferior simple seta blunt (Figure 30-34f), present on 

 far posterior setigers. Pharynx extending to setigers 4-6, margin 

 surrounded by ten soft papillae, dorsal tooth subterminal. Proventricle 

 extending from setigers 4-6 to 6-8, with 20 (15-31) rows of muscle cell. 

 REMARKS: Exogone lourei is remarkably similar to E. arenosa Perkins 

 (1981:1094, figs. 5g-j, 6) from Florida. It differs from the latter in 

 lacking a well-defined spine near the tip of the superior simple setae, 

 and in having a shorter proventricle with about 20 muscle cell rows 

 rather than up to 28. Gulf of Mexico BLM-OCS specimens can be separated 

 into two groups on the basis of proventricle length: those with 20 or 

 fewer muscle cell rows and those with close to 30. This dichotomy does 

 not persist with the superior simple setae. On the same specimen (re- 

 gardless of proventricle length), the superior simple setae may appear 

 either lacking a spine, or with a somewhat enlarged subdistal serration 

 which could be construed as a spine. In my opinion, these characters 

 are not sufficiently distinct or consistent to constitute a separate 

 species; thus the BLM-OCS specimens are retained as E. lourei , which is 

 herein newly reported from the Gulf of Mexico. 



PREVIOUSLY REPORTED HABITAT: Lower intertidal to 153 m; coarse sand, 

 mud, gravel with mud; between rocks among a colony of Fabr icia 

 oregonica . 



GULF OF MEXICO BLM-OCS OCCURRENCE: Widespread in northeastern Gulf 

 (Figure 30-33); 10-75 m; coarse to fine-very fine sand, silty fine to 

 ver, fine sand, clayey to sandy silt. 

 DISTRIBUTION: British Columbia to southern California, Gulf of Mexico. 



30-41 



