The small collection of Hydroids described in the present paper forms part of the marine invertebrate collections obtained by Messrs. C. Hedley and W. L. May, seven miles east of Cape Pillar, Tasmania, in December, 1907. The specimens are of interest as being the first samples of the Hydroid fauna of Tasmania from one hundred fathoms.
The specimens were dredged "on a firm bottom of sand, rolled pebbles, and a conglomerate of recent shells."
The collection is composed entirely of Calyptoblastic forms, and contains representatives of thirteen species, one of which is new.
The male corbulae of Aglaophenia tasmanica have been described for the first time, and an instance of sexual dimorphism has been observed in the structure of the corbulae of this species.
The most striking of the records of geographical distribution are as follows...