Colobonema sericeum is a species of deep-sea hydrozoan in the family Rhopalonematidae that was first described in 1902.

The animal in this image is a jelly called Colobonema sericeum. It belongs to a group of jellies called the hydrozoans, which lack the long, ribbon-like arms centrally located around the mouth of the jelly, which are characteristic of scyphozoans. Within the hydrozoan jellies, Colobonema belongs to a group called the Trachymedusae.