THUIAEIA PLUMULIFEEA. 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 THUIAEIA Fleming. 



Thuiaria distans. 



PI. XVII. Figs. 1, 2. 



Trophosome. — Stem attaining a height of about four inches, simple, non- 

 fascicled, sending off alternate pinna?, whicli extend from its distal end to 

 within a short distance of the base ; pinna? with transverse joints at distant 

 but uncertain intervals ; main stem with an oblique joint just above the 

 origin of each pinna. HydrothecfB distant, alternate, borne upon the stem 

 and pinna?, to each of which thej' 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. 



Tortiigas, shallow water. 



Thuiaria distans is remarkable for the length of the intervals by which 

 the hydrothec* of each side are separated from one another. The inter- 

 nodes of the stem are regular in length, and support each three hydrothecae ; 

 those of the pinnse are irregular in length, and vary in the number of hydro- 

 thecae to which they give support. 



The coenosarc of the stem is canaliculated. 



Thuiaria plumulifera. 



PL XVII Figs. 3-6. 



Trop/iosome. — 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 

 hydrothecae both upon their axis and pinnse ; pinnse alternate, much con- 

 tracted at their origin. Hydrotheca? alternate, deep, adnate for nearly their 

 entire length ; orifice with two strong, broad teeth, beyond which the walls 

 of the hydrothecae are continued as a thin, membranous, collapsible tube. 



Gonosome not known. 



Dredged off Cape Fear from a depth of 9 fathoms. 



