BULLETIN OF TIE 
136 
rising above the orifice of the hydrotheca. Mesial nematophore single, adnate, 
extending only a short distance up along the face of the hydrotheca. 
Gonosome ; — Phylactogonia springing from the proximal internodes of pinnæ 
on opposite sides of the stem. Number of phylactogonia twenty. Each phy- 
laetogonium with three branches formed by two bifurcations. The first of 
these bifurcations situated near the origin of the phylactogonium. Each branch | 
of the phylactogonium bears a single row of nematophores. | 
Gonangia affixed to the main stem and protected. by the branching phylacto- 
gonia. 
This species resembles closely C. ventricosus, Allman. A bottle of type 
specimens contains the hydroid figured by him, Pl. XXXI. fig. 1, and frag- 
ments which resemble C. compressus. 
In €. compressa the margin of the hydrotheca is simply toothed, and there 
is no prominent medially placed single spur as is found on the rim of the 
hydrotheca in (7, ventricosus (Allman, PL XXXI fig. 1). The hydrotheca is 
not ventricose, as in C. ventricosus, and the whole trophosome is smaller. 
St. Vincent, 114 fms. 
PLEUROCARPA, n. g. 
The characteristic of this genus is a peculiar gonosome, which is formed 
from. the proximal portion of a branch, while the distal end of the same retains 
the true character of the branch and bears pinnæ. Gonosome a corbula, 
Pleurocarpa ramosa, n. $. 
Hydrosome: — Hydrocaulus branching, eight to ten inches high. Stem 
stout, non-fascicled. The branches bear medially placed rows of nemato- 
Pinne jointed, alternate, arise from upper surface of the branches. 
phores. 
margin toothed. 
Hydrothece closely approximated on the pinna, short, thick, 
Intrathecal ridge prominent. Mesial nematophore in distally placed hydro- 
thecæ, adnate along the whole face, and continued beyond the orifice of the 
hydrotheca. In proximal hydrothecæ, however, although adnate along the face 
of the hydrotheca, the mesial nematophores seldom rise above the margin, 
tonosome: — Corbula open, formed by many rib-shaped pinna on the prox- 
imal end ofa branch. Each rib is destitute of hydrothecæ, and covered with 
tubular nematophores, which project at right angles to the axis of the rib from 
all sides. Proximal end of the branch of which the corbula is a modification 
destitute of pinnæ, forming a peduncle for the gonosomes. It bears seve ral | 
hydrothecæ. The branch beyond the corbula bears many alternately arranged | 
pinnæ, with hydrothecæ, not unlike a normal branch of the trophosome. 
St. Vincent, 95 fms. 
This genus proves without doubt that the structure called a corbula is in 
some cases a modified branch, and not, as Allman has shown to be true 
in some genera, a modified pinna. According to Allman, the ribs of the 
