PLATE IV. 
Figs. 1-3. — Halecium arboreum [robustum] 1 (p. 10). 
Fig. 1. — An entire colony; natural size. 
Fig. 2. — Portion of a colony; magnified 15 diameters. 
Fig. 3. — A hydrophore, showing its basal segment adnate by its epicauline side to the 
supporting internode, and its very narrow limbus ; magnified 20 diameters. 
1 It lias been found necessary to change the name since the plate was printed off. 
