HYDROZOA 127 
over the fronds of seaweeds, often crossing and recrossing in a tangled 
mass. At short intervals the upright, straight branches rise to one inch 
or one and a half inches in height, and are more or less branched. All 
except the creeping stems are close set on each side, with cylindrical 
zooid-eups which turn outward at the ends. The cups of the reproduc- 
tive zodids are not sessile; they are much larger than those of the nutri- 
tive ones and are urn-shaped. (Plate XLII, A.) 
S. argentea. This is a beautiful species, common from New Jersey 
northward. It has a profusion of silvery branches on a dark stem. The 
colonies are often a foot or more long, and the branches at the top and 
bottom of the stem are shorter and fewer than those in the middle of 
the colony. The zodid-cups are nearly cylindrical, pressed closely to the 
stem, nearly opposite or subalternate to one another, and end in 
pointed tips. The medusa-bud is urn-shaped, with two horns at the top. 
(Plate XLII, B.) 
S. cupressina, the sea-cypress. This species is similar to S. argentea, 
but the main stem is thicker and longer, and the branches less crowded 
and less subdivided. The branches are arched or drooping, instead of 
straight, and gradually decrease in length at some distance from the 
lower and upper parts of the stem, giving a spire-like apex, the stem 
often continuing into a bare, branchless extremity. The zodid-cups are 
tubular, not much narrowed or divergent above, and two-lipped on the 
margin. It is found from New Jersey northward. (Plate XLII, B.) 
THE PLUMULARIANS 
These hydroids are feather-like in the manner of branching, 
short lateral branches being arranged on each side of a long cen- 
tral stem. In some species the stems are naked below and 
resemble quills. The zodid-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 asmall ostrich-plume. The zodid- 
cups are arranged in a single row on one side of each snort 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 
ealled nematophores, and are supposed to be degenerate zooids. At inter- 
vals a branch is replaced by a cylindrical body covered with nemato- 
phores, and in these the generative zodids 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 
