Endoceratidss

Endoceratidss, an extinct family of Cephalopoda, including Endoceras, a genus remarkable as the siphuncle (q.v.) is protected by a thick tube formed by the septa being prolonged backwards around it. Endoceras is found only in the Lower Silurian (Ordovician), except one doubtful species, but its ally Piloceras also occurs in the Cambrian.