ARGULUS. 
247 
body, and extend downwards, covering a portion of the 
thorax. The line of separation between these lateral 
lobes and the anterior division is very distinctly to be 
seen, forming a mark like the letter Y. In the anterior 
portion we see the eyes and the brain shining distinctly 
through the shell, and in the latero-posterior portions we 
trace a highly-coloured series of ramifications, springing 
from a trunk which comes direct from the stomach. 
The eyes are lodged in the thickness of the shell, and 
appear as two dark spots placed at a little distance from 
each other. They are situated on the upper part of the 
anterior portion of the carapace, are immoveable, of a 
spherical form, and of a very deep violet colour. Each 
eye is inclosed in a membranous sac, and, like the eyes of 
the Branchiopodae, are areolar. 
The brain appears in form of a small black point, situate 
behind the eyes, and consists of three lobes, of about equal 
size. Nerves are given off from this mass, which may be 
seen running down, to supply the abdomen and natatory 
kgs. 
The antennae (t. XXXI, f. a) are situated in front of 
the eyes, and are completely concealed under the anterior 
edge of the carapace. They are short and stout, consist- 
ing of two joints. The basilar joint is broad ; the terminal 
equally broad at the base, gradually tapers to a point, 
and terminates in a curved horn-like point. This joint 
has, on its external edge, a slender appendage, three- 
jointed, directed outwards, and extending beyond the 
branch from which it springs. Arising close to the base 
of these antennae we find a pair of organs (t. XXXI, f. 5), 
which have been described by Jurine, and Dana and 
Herrick, as a second pair of antennae. They are smaller 
than the antennae, and consist of four articulations. The 
basilar joint is large, and the other three gradually become 
smaller and smaller, the apical one terminating in three 
or four very small spines. The anterior pair of these 
organs is described bv Cuvier as the mandibles. Jurine 
considers them as organs by means of which they assist 
