HYDEOIDS OF THE HAWAIIAN ISLANDS. 
953 
particular, the hydrothecate internodes ending in a straight upper and an oblique lower node and 
bearing a hydrotheca near the middle or a little below. Hydrothecse rather deep cup-shaped, margin 
even, about half of adcauline side free from the hydrocladium. 
Supracalycine nematophores scarcely reaching the hydrothecal margin; 4 to 6 mesial nematophores 
between adjacent hydrothecse. 
Gonosome. — Gonangia pyriform, with a round margin, large terminal aperture and 2 nematophores 
on the short pedicel. They are borne at the bases of the hydrothecse. 
Localities. — Station 3854, south coast of the island of Molokai, 30 fathoms; station 3859, between 
the islands of Molokai and Maui, 138 fathoms. 
This species is of peculiar interest, as it shows the manner of forming a stem by the aggregation 
of root-stocks. I have elsewhere shown that the peripheral tubes of the fascicled stem in many 
species are formed by modified hydrocladia. « 
The student of the Hydroida is continually having the extreme plasticity of these organisms forced 
upon his attention, and this plasticity, with its complementary lack of fixity, is the cause of untold 
confusion in the systematic discussion of the group. 
Genus AGLAOPHENIA. 
Trophosome. — Hydrothecal margin dentate; a posterior intrathecal ridge present; 3 nematophores 
attached to each hydrotheca. 
Gonosome. — Gonangia inclosed in true corbulse, the leaves of which do not bear hydrothecse at 
their bases. 
? Aglaophenia rigida Allman. 
A single fragmentary specimen, without gonosome, found at station 4072, north coast of the island 
of Maui at a depth of 52 fathoms, is referred, with considerable doubt, to this species. Another 
fragment was secured at station 3847, south coast of Molokai Island, 23 fathoms. 
Aglaophenia rigida Allman, Mem. Mus. Comp. Zool., V, 1877, No. 2, 43. 
Genus THECOCARPUS. 
Trophosome. — Stem fascicled, hydrothecse toothed, nematophores attached to the hydrothecse. 
Gonosome. — Corbula composed of separated leaves, each of which bears a hydrotheca near its base 
on its outer side. More than one hydrotheca between the corbula and the stem. 
Thecocarpus niger Nutting, new species. 
(PI. v, fig. 5; pi. xiii, figs. 1-6.) 
Trophosome. — Colony black in color, attaining a height of about 6 inches. Stem fascicled, proximal 
portion unbranched, distal part giving off a number of irregularly disposed large branches which 
themselves often branch in an irregular manner; smaller branches not fascicled, and the internodes not 
apparent unless the specimen is boiled in potash, when a regular division into short nodes divided by 
oblique internodes is apparent. Hydrocladia alternate, borne on front of stem and branches, divided 
into regular internodes, each of which bears a hydrotheca and shows an internal chitinous ridge at 
about its middle. Hydrothecse ovoid in shape, margin with about 10 irregular jagged teeth, the points 
of which turn inward, the anterior one forming a horn-like projection rising somewhat above the 
others; intrathecal ridge low and straight, nearly horizontal. Supracalycine nematophores horn-like, 
not very large, rising about to the top of the hydrotheca; mesial nematophore arising above the middle 
of the hydrotheca, projecting outward and upward, not attaining the level of the top of the hydrotheca, 
and with two apertures; cauline nematophores large, 2 at the base of each hydrocladium. 
Gonosome. — Gonangia contained in a corbula bearing a close resemblance to that characteristic of 
Aglaophenia, but really of the Thecocarpus type. It is very large, gracefully arched, with the concave 
side upward, composed of 18 to 20 pairs of corbula leaves, each of which bears a hydrotheca near its 
base on the outside and 2 rows of large tubular nematophores with conspicuous nematocysts. The last 
2 or 3 pairs of leaves are represented by hydrothecse alone, and 1 or 2 hydrothecse are found on the 
stem between the first true corbula leaf and the stem from which the corbula springs. 
a American Hydroids, Part II, p. 5, 1904. 
