THUIARIA PLUMULIFERA. 27 
true Sertularia; while the resemblance of this part of the hydroid to a Ser- 
tularia is further increased by the occurrence of a deep constriction be- 
tween each internode. 
Genus THUIARIA FLEmtine. 
Thuiaria distans. 
EE OV, Bigs. V, 2: 
Trophosome. — Stem attaining a height of about four inches, simple, non- 
fascicled, sending off alternate pinnz, which extend from its distal end to 
within a short distance of the base ; pinne with transverse joints at distant 
but uncertain intervals; main stem with an oblique joint just above the 
origin of each pinna. Hydrothecz distant, alternate, borne upon the stem 
and pinne, to each of which they are adnate for very nearly their entire 
height; short, tubular, slightly enlarging upwards and bending outward, 
with a somewhat wavy margin destitute of teeth, and with a narrow, though 
distinct border. 
Gonosome not known. 
Tortugas, shallow water. 
Thuuria distans is remarkable for the length of the intervals by which 
the hydrothecz of each side are separated from one another. The inter- 
nodes of the stem are regular in length, and support each three hydrothece ; 
those of the pinne are irregular in length, and vary in the number of hydro- 
thecx to which they give support. 
The coenosare of the stem is canaliculated. 
Thuiaria plumulifera. 
Pl. XVII Figs. 3-6. 
Trophosome. —Stem attaining a height of about six inches, slender, flexile, 
emitting numerous pinnate branches which are disposed from distance to 
distance rather irregularly on all sides of the stem, and which carry the 
hydrothece both upon their axis and pinne ; pinne alternate, much con- 
tracted at their origin. Hydrothece alternate, deep, adnate for nearly their 
entire length ; orifice with two strong, broad teeth, beyond which the walls 
of the hydrothece are continued as a thin, niembranous, collapsible tube. 
Gonosome not known. 
Dredged off Cape Fear from a depth of 9 fathoms. 
