1910] Robertson: Cyclostomatous Bryozoa. 259 



Zoarium erect, composed of short, divergent, cylindrical 

 branches, frequently dividing dichotomously and terminating in 

 blunt rounded extremities. When the branches closely approx- 

 imate each other, they frequently coalesce, giving the whole 

 colony a complexly reticulated appearance (pi. 25, figs. 51 and 

 52). Zooecial aperture (fig. 53, zoe. ap.) circular, large, sur- 

 rounded by numerous (6-8) smaller, variously shaped pores, the 

 openings of the interstitial canals (inter, run.). Surface, except 

 toward the tips of the branches, covered with a delicate calcareous 

 layer which hides the interstitial pores i fig. 54) but which exci p1 

 in the oldest parts of the colony leaves the zooecial apertures 

 unimpeded. 



Living Heteropora has been reported from comparatively few 

 localities, viz., from the neighborhood of Japan and Australia by 

 Waters, from New Zealand by Busk, and from Vancouver Island 

 by Whiteaves. Busk has expressed the opinion that 

 //. neozealanica may prove to be identical with the Japanese 

 species. II. pelliculata, and Whiteaves regards the species found 

 on Vancouver Island as similar in all respects to the Japanese 

 species. In our collection Heteropora has been obtained from 

 several localities from Alaska southward. One specimen found 

 on Channel Rock, Puget Sound, was a clear lemon yellow when 

 living, the color soon disappearing when placed in alcohol. This 

 colony, in a perfect state. was about five centimeters high and 

 somewhat broader, and is remarkable for the complexity of its 

 branching, the anastomosis which has taken place giving it a 

 highly reticulated appearance (fig. 51). The surface is covered 

 by a thin calcareous layer (fig. 54) so that the pores of the 

 interstitial canals are not discernible over most of the surfacS. 

 On the inner protected portions of the surface the zooecial tubes 

 project to a marked degree, but on the exposed portions they 

 are almost level with the surface of the branch. The other 

 colonies obtained are of a somewhat stouter habit of growth 

 and show less anastomosis, as a rule (fig. 52). In all of these 

 the polypides and the tissue lining the zoceeia and interstitial 

 canals are purplish, and the colonies after long immersion in 

 alcohol are of a dark color. 



H. pelliculata is probably abundant on the western coast of America. 



