442 



ISOPODA. 



NORM A LI A. 



Genus LIGIA. (Fabricius.) 



Generic character. External antennae long, with a multi- 

 articulate flagellum. Terminal pair of uropoda with the basal 

 portion exserted backwards, truncated at its extremity, to 

 which are affixed a pair of elongated cylindrical rami. 



THE head is small, its anterior margin forming a con- 

 tinuous arched line with the sides of the first segment of 

 the body. 



" When the head is looked down on from the front, we 

 remark anteriorly, just beneath, but not attaining to the 

 frontal line of the head, a broad plate extending over 

 the entire forehead, and divided transversely by a raised 

 ridge ; its superior margin is also marked by a raised 

 ridge. This superior ridge passes off on each side 

 beneath the eyes, forming at least a third of the inferior 

 border of the orbit. The external angle of the orbit, 

 however, is formed not by this, but by the cephalic ring 

 continued forward from behind, and terminating as a 

 rounded knob just above the external antennas ; these 

 arise in the angle between the inferior border of the 

 frontal plate and the projecting lobes. The inferior 

 border of the frontal plate is formed of two curves, 

 convex upwards, one over the origin of each external 

 antenna ; the angle of their junction is truncate, sepa- 

 rated by a short transverse suture from a small, narrow, 

 somewhat quadrilateral plate, which bears the internal 

 antennae, and is probably the remains of the second or 

 internal antennary ring ; the frontal plate itself repre- 

 senting the external antennary or third ring of the typical 

 crustacean. Beneath is a broad, well-marked plate, the 

 epistome." Kinahan, op. cit. p. 264. 



