Graptolitidæ (GRAPTOLITOIDEA or RHABDOPHORA)

Fo il Hydrozoa with compound hydrosoma, sometimes branched, bearing numerous polypites, protected by hydrothecæ and united by cœnosarc. All is inclosed in a tubular polypary, sometimes strengthened by a solid axis. They were generally free-swimming. They are delicate forms, allied to Sertularians. The polyps may be on one side or both sides of the stem. Traces of a pneumatophore have been found. Grappling Iron.