Body up to 5 mm long; carapace often mottled with grey.
Cephalothorax tapered and truncate anteriorly, slightly narrowed posteriorly.
Pereionites with rounded margins, pereion segment 1 much shorter in length than the succeeding segments. Antenna 1 with 4 articles, antenna 2 with 7 articles, the distal 2 very short. Lacinia mobilis of the left mandible well developed, that of right mandible reduced.
Chelipeds variable in form - in some specimens a tooth-like process is seen on the inner margin of both the propodus and dactylus, in others one or both of these processes may be absent. Cheliped often rather stronger in male.
Pereiopods 4-6 similar; dactylus and unguis fused to form a claw which bears a row of comb-like setae and also small setose tufts on its proximal margin.
Uropods with three-articled endopodite.
T. dulongii is a common species in the littoral and shallow sublittoral, where it inhabits self-constructed tubes of sand grains, mud and detritus.
It has been found between northern Norway and the Mediterranean, from the east coasts of North America and South America, and from south-west Australia.