EXPLANATION OF PLATE IV. 
Fic. 1.—Hebella crateroides, Ritchie. Portion of colony, showing 
both trophosome and gonosome, X 35. 
2.—Sertularella polyzonias, var. cornuta, Ritchie. Portion of 
branch with gonotheca, X* 25. 
3.—Diphasia mutulata (Busk). Portion of stem with hydro- 
theese < 35: 
4.—Diphasia thornelyi, Ritchie. Portion of stem with hydro- 
thece, front view, X 50. 
5.—Diphasia thornelyi. Portion of stem bearing gonangia, 
seen partly from the side, X 50. 
6.—Aglaophenia septata, Ritchie. Portion of hydroclade, 
x 45. 
7.—Aglaophenia septata. Gonosome, X 13: br.l., branchlet. 
of lower tier; bry.up., branchlet of upper tier; gon., 
gonangium ; 7., ridge at base of upper leaflets pro- 
jecting over gonangia ; ch., chitinous plate. 
8.—Lytocarpus annandalet, Ritchie. Portion of stem show- 
ing bases of hydroclades, * 35. 
g.—Lytocarpus annandalei. Portion of hydroclade, X 60. 
10.—Lytocarpus annandalei. Phylactocarp, X 30. 
11.—Lytocarpus pennarius (Iinn.). Portion of hydroclade, 
x 70. 
12.—Halicornana bale, var. flava, Nutting(?). Portion of 
hydroclade, X 70. 
13.—Halicornaria Mians, var. profunda, Ritchie. Portion of 
hydroclade with hydrothece at a late stage of develop- 
ments "70; 
14.—Halicornaria hians, var. profunda. Portion of hydroclade 
with hydrothecee at an early stage of development, X 70. 
