20O NUTTING [182] 



HALECIUM ROBUSTUM sp. nov. 

 (Plate XXIII, figs. 3, 4, 5.) 



Trofhosotne. — Stem very thick and fascicled, consisting of an im- 

 mense number of wavy tubes. In the single specimen collected, the 

 main stem divides near its base into three heavy fascicled branches, 

 which themselves branch and subdivide extensively, the fasciculation 

 continuing nearly to the tips of the branches. The entire height of 

 the colony is about three inches. The branching is so profuse that the 

 arrangement of the internodes is obscure. The ultimate branches give 

 off short pedicels and sessile hydrophores in what appear to be clusters 

 or whorls. Pedicels short, tubular, ending in an exceedingly shallow 

 hydrophore. Hydrophores reduced to a mere narrow rim, marked by 

 the internal diaphragm and circlet of dots, the only distinction between 

 pedicel and hydrophore, as the margin of the latter is not appreciably 

 everted. Most of the hydrophores are sessile, being set on mere 

 shoulders of the branch from which they grow. The circlet of dots 

 can only be made out with great difficulty and the use of high magnifi- 

 cation. Hydranths exceedingly numerous and large, covering the 

 branches so as to almost entirely conceal them from view. Tentacles 

 about twenty, surrounding a low conoid proboscis. 



Gonosome. — Unknown. 



Distribution. — Berg Inlet, Glacier Bay, Alaska (Harriman Ex- 

 ped.). 



This species bears some relation to Halecium densutn Calkins, ' but 

 differs from that species in the hydrophores, which are not reduplicated 

 and have straight, not everted, margins. The hydranths are so crowded 

 that a branch resembles an expanded colony of Alcyonaria, and appears 

 to be made up entirely of hydranths. 



Family SERTULARIDy^. 



Trophosome. — Hydrothecae sessile, more or less adnate by their side 

 to the stem and branches upon which they grow ; always in more 

 than one longitudinal row on each branch, the arrangement usually 

 biserial. Hydranth with a conical proboscis. 



Gonosome. — Reproduction always by means of planula», which are 

 developed within the gonangia. No medusae. 



SERTULARELLA. 



Trophosome. — Stem and branches divided into regular internodes, 

 each bearing one or two hydrothecae ; nodes oblique. Hydrothecae 

 'Proc. Boston Soc. Nat. Hist., Vol. 2S, no. 13, p. 343, 1899. 



