Microscopical Society of Victoria . 
20 
opening in front appears to represent the ordinary lateral aperture, 
and the repetition of the terminals is similar to what occurs in 
A. plumosa , where the proximal sarcotliecae of the gonangial 
pinnules frequently bifurcate about the middle, thus presenting 
two terminal orifices. 
Altogether, I have ten species from our own shores and two 
from Port Darwin, and in all, except A. parvula , the lateral and 
terminal apertures are separate in the mesial sarcotliecae, while in 
the laterals they are separate in all except A. parvula and 
A . Thontpsoni \ and in both these species the form of the aperture 
shows plainly that they are the result of the union of the ordinary 
terminal and lateral orifices. I have seen only one species in 
which the sarcotheca) show no indication of the lateral aperture— 
a species closely allied to A. myriophyllum , if not identical with it. 
Its locality is unknown, but it probably came from the seas to 
the north of Australia. The absence of lateral orifices in this 
form is explained by the fact that the sarcotliecse are all truncated 
so far down that the terminal orifices are below the point at 
which the laterals are usually found. On the whole, it would 
appear that the species with lateral and terminal openings to each 
sarcotheca represent the typical aspect of the genus, and that the 
lateral apertures are oidy wanting when the shortness of the 
sarcotheca causes them to be completely merged in the terminal 
ones. Even in species which have usuaLly more than one orifice 
to the sarcotliecse it frequently happens, when these are short, 
that the orifices are united by a fracture-like opening. The 
lateral apertures appear to be the more constant of the two, as, in 
several of our species, the sarcotliecse of both kinds near the 
distal ends of the pinnae are frequently found with the ends closed 
and entire, while the lateral orifices are open. In these cases, the 
mesial sarcotheca is usually shorter than the ordinary open- 
pointed ones on the other portions of the polypidom, but the 
laterals, on the contrary, are apt to be much longer and stouter, 
either with or without the suppression of the terminal orifice. 
The form which I have described as A. parvula is peculiarly 
interesting from the structure of the corbula, which, in some 
cases, is formed on the type of A. pluma , or rather A. tubulifera , 
and in others consists of free leaflets or broad pinnules, with a 
series of sarcotliecse fringing each margin. These different modi- 
