These hydroids are feather-like in the manner of branching, short lateral branches being arranged on each side of a long central stem. In some species the stems are naked below and resemble quills. The zoöid-cups are only on one side of the short branches. (Plate XLIII.) GENUS ^Aglaophemia^ ^A. struthioides^, the ostrich-plume. This species, which is found on the Pacific coast, is perhaps the most beautiful of the hydroids. It varies in size and color, but always suggests a small ostrich-plume. The zoöid-cups are arranged in a single row on one side of each short branch, and the main stem has a joint between each of the branches, which are placed quite close together. The rims of the cups have sharp-pointed teeth, and from the top emerge three tubular projections, which are called /nematophores/, and are supposed to be degenerate zoöids. At intervals a branch is replaced by a cylindrical body covered with nematophores, and in these the generative zoöids are developed. (Plate XLIII.) GENUS ^Plumularia^ ^P. falcata^ (Johnston), or ^Hydrallmania falcata^ (Hincks). This species is found on shells and rocks near low-water mark from Long [pg128] Island Sound northward. It is from four to twelve inches high. The main stem is in long spiral turns, and at intervals has spreading plumose branches. The zoöid-cups are tubular and closely pressed against one another, and are ranged in rows on one side of the branchlets; the apertures of the cups are plain and oblique. (Plate XLIII.) FAMILY ~GERYONOPSIDÆ~ GENUS ^Tima^ ^T. formosa.^ A very delicate and transparent medusa; size one to two inches in diameter; bell conical; radial tubes four in number; manubrium long, hanging far below the disk; four frilled appendages diverging from the corners of the mouth; tentacles thirty-two; egg-sacs white and following the line of the radial tubes in undulating folds. This species is not very common; it is found on the New England coast. FAMILY ~ÆQUOREIDÆ~ GENUS ^Zygodactyla^ [Illustration: /Zygodactyla groenlandica./] ^Z. groenlandica.^ Medusa seven to eleven inches in diameter; disk violet-colored and transparent; margin fringed with long, fine, contractile tentacles of a darker violet color; numerous radiating tubes; egg-sacs in slightly waved plates; manubrium hanging below the line of the disk and with a thin frilled membrane depending from it. Found north of Cape Cod in July. ORDER =TRACHYLINÆ= The /Trachymedusæ/ are characterized by their direct development, the egg of the jellyfish producing a medusa and not a hydroid colony. GENUS ^Trachynema^