Mesogloia hudsonii Nemalion helminthoides is a small marine alga in the division Rhodophyta.

This is a fairly large erect alga which grows to no more than 0.4 m long.

It is very mucilaginous and with few branches which are elongate growing from a discoid base.

The central strand is composed of filaments intricately entangled.

[1] The spelling of the specific name is in older references spelt without the first letter "h".