Greville^ on Asterola7npra. 
103 
justify De Brebisson in using the terms celluloso-reticulate, 
subpunctulate^ subgranulate^ &c.^ in order to describe the 
relative appearance of the segments under the same magni- 
fying power, it was easy to see by sufficiently increasing the 
power that the structure of all was essentially the same. 
In the preparation of the present communication, I gladly 
acknowledge the valuable suggestions I have received from 
my friends. Professor Walker-Arnott and Mr. Eoper. 
As some confusion already exists with regard to the names 
applicable to the different parts of these discs, it is desirable 
that some attempt should be made to regulate them. I ven- 
ture, therefore, to propose the following nomenclature, which 
will be followed in this paper, and easily understood with the 
help of the following diagram : 
Kg. 1. Fig. 2. 
Fig. 1, diagram of Asteromphalus ; Fig. 2, diagram of Spa- 
tangidium. To convert Fig. 1 into a diagram of Asterolam- 
pra, all that is required is to separate the lines cc a little, and 
make the ray / as broad as the rest. 
a umbilicus, b umbilical lines, c median lines (approximated 
umbilical lines), d hyaline area (composed of the united bases 
of all the rays), e rays, /median ray, g areolated segments. 
A few explanatory remarks may be required with reference 
to some of these terms. It has been suggested that " hyaline 
area is uncalled for, because it is composed merely of the 
bases of the rays. This is true, but it is composed of the 
bases of the rays collectively, and it will be very convenient 
sometimes to be able to define the contour, position, &c., of 
this area. As to the rays themselves, there can be no doubt 
