Cx 
Or 
ROUNDHEADS 
CHAPTER VI 
TRIBE I,—CYCLOMETOPA 
THE name literally means ‘those of a circular forehead.’ 
In these Crustacea the carapace is often of a breadth 
greater than the length, wide and regularly arched in 
front, more rarely quadrate or suborbicular, but not 
rostrate. The epistome is short, transverse. ‘The first 
antennz are in general transversely folded. The third 
maxillipeds have the fifth joint articulated at the apex or 
the inner front angle of the fourth (except in Pirimela). 
There are nine pairs of branchiz, with their efferent 
channels opening at the sides of the endostome or palate. 
The verges of the male are inserted at the bases of the 
last legs of the trunk. 
Milne-Edwards states that the different ganglia of the 
trunk form a sort of circular ring, of which it is often easy 
to distinguish the constituent elements, and that the two 
halves of the liver remain distinct without a median lobe. 
The tribe has been subdivided into four legions— 
Cancrinea, Cyclinea, Corystinea, Thelphusinea, m de- 
fining which I shall follow the safe guidance of Mr. E. J. 
Miers, as afforded in his report on the Brachyura collected 
by the Challenger. 
Legion 1.—Cancrinea. 
The buccal cavity is usually well defined. The flagella 
of the second antennz are not greatly elongated. ‘The 
seventh joint in the walking-legs is generally unarmed. 
It is either stiliform or in the Jast pair expanded into an 
