I can provide only the family (Sabellariidae) with around 123 species!! 

I guess it is from the Meditteranean?

perhaps Owenia, although in this genus the tube is more curved ? It doesn't look like Pectinariidae to me.

Thanks Eva-Lisa, thanks Tom.

The sand pipe does not come from the Mediterranean, but you do not know the exact origin. The curvature is light but well visible, the dimensions are quite remarkable, but the most unusual feature is the position of the grains.

Photos on internet suggest obligate use of sand grains as building material in tubes of members of the Pectinariidae family. However, this is not the case. These polychaetes use materials depending on local availability (Rouse & Pleijel 2001). Tubes may not only be constructed of sand grains but also of shell fragments and foraminifera, in a one- or two-layered arrangement (see references in Moreno et al 2004). Particles either abut or overlap (Rouse & Pleijel 2001). Tubes are characteristically cone-shaped, often bent like the photo of this question. The tube on the photo is built for a large part by small discs, most probably foram skeletons. So I believe this is a tube of a pectinarian polychaete. It would be nice to know somewhat more of the sampling location and depth.

Book Polychaetes

Article Pectinaria chilensis Nilsson, 1928 (polychaeta: Pectinariida...

 THANKS Godfried,  the suggestions are very useful to bring the solution to this research closer

It's a serpulid worm tube. Go to my ResearchGate page and see this paper: Finger, K.L., Flenniken, M.M., and Lipps, J.H., Foraminifera used in the construction of Miocene polychaete tubes, Monterey Formation, California, USA. Journal of Foraminiferal Research, 38(4): 277–291.

Thanks Kenneth, you suggested a paper that has provided me with a good refinement for the research.

Massimo

It is not a serpulid tube (are calcareous), it's a Pectinariidae tube formed with sand grains.

Duh! Of couse it's not a serpulid -- I don't know why I said that. Pectinarid it is, just like had in the paper thatI I referred to.

Yes, I think it is in the family Pectinariidae, looks very much like Pectinaria gouldii that lives on the Atlantic coast of the USA.

It's a Pectinariidae tube.

Thank you, I had news about the place of origin, 

he probably comes from Philippines

This sandbox belong to a Polychaeta of the Genus Pectinaria.

The next time I try to identify the exact species.

thank you Roberto

Many of us agree that it is the case of a polychaete of genus Pectinaria, unfortunately we do not have the specimen, it was never found. Two clues remain: most of the shell is build in whit foraminifera, collected from bottom where polychaete lived; furthermore, inside the shell there are dried remains of the specimen, would you be able to withdraw ADN for research in molecular biology?