Aspidosiphon (Aspidosiphon) exiguus Edmonds, 1974  

This is an interstitial species collected in the intertidal zone in Cuba. The largest worm is 4.5 mm in trunk length and the introvert can be up to five times the trunk length. The anal shield is ungrooved,consisting of small, pale units, and has up to four cone shaped papillae on the anterior ventral border. The caudal shield is weakly developed and occasionally absent.