EOUNDHEADS 55 



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 

 antennas 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 branchias, 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, in 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 antennaa are not greatly elongated. The 

 seventh joint in the walking-legs is generally unarmed. 

 It is either stiliform or in the last pair expanded into an 



