Body small, firm, with long tail segment, opaque. Head small. Teeth in two rows, anterior teeth longer than the posterior. Eyes pigmented. One pair of lateral fins, entirely on the tail segment and completely rayed. Tail fin spatulated. Collarette begins on the head and extends to the lateral fin. Alimentary diverticula present.
Ovaries short and broad, with large ova. Seminal vesicles large and round, touching both the lateral and tail fins. Ventral side of tail with glandular areas and adhesive papillae.
Hooks: 7-10. Teeth in two rows, 3-5 anterior, 2-4 posterior.
Maximum body length 5.5 mm; relative tail length 49-58%.
S. cephaloptera is not a strict planktonic species, but lives benthically. It occurs in shallow waters from 0 to about 100 m depth.
Distribution in the North Sea
Whole North Sea, adhered to rocks, algae, etc.
Benthic, coastal in NE Atlantic. Also reported from Australia and Japan; probably widespread in shallow coastal waters.
[After Pierrot-Bults and Chidgey, 1988]