1903.] BROOKS—NEW GENUS HYDROID JELLY-FISHES. 18 
below, and equal in number to the terminal branches of the radial 
canals. All of these pockets open at the same level below, but the 
sixteen pockets of the fourth set are very shallow, the eight pockets 
of the third set and the four of the second set are deeper, and the 
four primary pockets of the first set reach nearly to the apex of the 
subumbrella. The primary tentacles are stout, hollow, contractile, 
and when the jelly-fish is swimming they are stiffly extended with 
their tips coiled into compact spiral whorls. There are sixteen of 
these tentacles in every specimen that I have examined. The 
young specimen which is shown in Fig. 2 has sixteen distal radial 
canals, and a hollow tentacle arises from the circular canal in the 
plane of each branch of each radial canal. In the older specimen 
which is shown in Fig. 1 the hollow tentacles are still sixteen in 
number, although the distal canals are twice as numerous and 
although the hollow tentacles are now in the radii of dichotomy 
instead of being, as they are in the younger specimen, in the radii 
of the distal branches. The solid tentacles are short with little 
power of extension or contraction; they are usually turned out- 
ward and upward over the margin of the bell, and they remind one 
of the solid tentacles of the Geryonidz. In all the specimens 
that I have examired they are equal in number to the distal 
branches of the radial canals: sixteen in the young jelly-fish shown 
in Fig. 2, thirty-two in those with thirty-two canals and thirty- 
three in the one shown in Fig. 1. 
Color.—The gonads and the manubrium of old specimens are 
opaque white. The bell and the subumbrella and the tentacles 
are nearly colorless. The radial canals, the circular canal and the 
axes of the hollow tentacles are colored in young specimens by 
pigment-granules of a brownish-orange. 
Size. —The bell is about one-third of an inch high and a little 
less than one-fourth of an inch in diameter. 
Locahty.—Several specimens were taken at high tide in an inlet 
from the open ocean in the Bahama Islands, near Nassau, in 1887, 
and at Bimini and at Green Turtle, in the Bahama Islands, in 
1886 and 1888. It is common and widely distributed among the 
Bahama Islands. 
If the analytical key which Haeckel gives in his System der 
Medusen were to be followed, the genus Dichotomia would belong 
among the ‘‘ Leptomedusz,’”’ in the family Cannotidz, in the sub- 
family Williadz, and in or near the genus Proboscidactyla (System 
