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 V. 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 conies 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 Branchiopodse, 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 clown, to supply the abdomen and natatory 

 legs. 



The antennae (t. XXXI, f. ci) 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. b), 

 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 by Cuvier as the mandibles. Jurine 

 considers them as organs by means of which they assist 



