36 MONOSTAECHAS. 
supracalycine nematophores, and with azygous nematophores along the 
hydrothecal side of the ramulus. 
Gonosome not known. 
The genus Hippurella unites in itself the characters of a Plumularia 
and of an Antennularia or Antennopsis. Indeed, the genera Plumularia, 
Antennularia, Antennopsis, and Hippurella differ from one another mainly 
in the disposition of the ultimate ramuli. The characters thus afforded 
have long been recognized as of generic value in the separation of 
Antennularia from Plumularia, and the application of the same principle 
to other forms necessitates the construction of Antennopsis and Hippurella 
as legitimate genera. 
Hippurella annulata. 
Pl. XXI. Figs. 7, 8. 
Trophosome. — Hydrocaulus attaining a height of about three inches, 
springing from a dense bundle of tubular filaments, fascicled throughout 
the main stem, which sends off numerous non-fascicled branches, which 
are pinnately disposed below, but given off irregularly towards the distal 
end of the hydrocaulus; ultimate ramuli alternate and pinnate towards 
the proximal ends of the branches, but towards the distal ends surround- 
ing the branch on all sides, and here either scattered or regularly verticil- 
late ; each composed of alternate long and short internodes with inter- 
vening groups of very short ring-like internodes, each. of the long internodes 
carrying a hydrotheca. Hydrothece deep, thimble-shaped, with slightly 
everted margin. Besides the supracalycine pair of nematophores, there 
are two mesial nematophores, borne by the ramulus, between every two 
hydrothece. 
Gonosome not known. 
Off Pacific Reef from a depth of 283 fathoms. 
The species is rendered striking by the large size and deep thimble- 
shaped form of its hydrothecee, and by the annulation, at intervals, of its 
ultimate ramuli. 
MONOSTAZZCHAS ALitman nov. gen. 
Generic Cuaracter. Zyophosome.— Stem branched ; hydrothecal ramuli 
confined toone side of their supporting branches. Hydrothece unilateral 
