164 BRITISH OOPEPODA. 



the male are crenulated ; so also is the anal operculum 

 (fig. 14 a), the lower border of the last abdominal 

 segments (6), and of the thoracic segments (fig. 12). 

 Caudal segments broader than long, bearing three 

 principal setse, the innermost of which is stout, and 

 about half the length of the abdomen, the outer very 

 much shorter. Integument thick and closely per- 

 forated (fig. 35). Colour yellow, the hinder portion 

 of the first segment, and the abdomen, tinged with 

 brown or orange, the last thoracic and margins of 

 first abdominal segment with bluish purple. Length 

 Yg-th of an inch (1 mm.). 



Apparently a very local species. On Algas near low- 

 water-mark at St. Mary's and St. Agnes (Scilly 

 Islands), where it was also taken in the surface-net in 

 the evening. A few specimens only amongst roots of 

 Algas between tide-marks at Eoundstone, Connemara. 



Sub-family 8. POEOELLIDIIN.E, Boeck. 



Body much depressed; secondary branch of pos- 

 terior antenna 1 -jointed; mandible-palp forming a 

 large setiferous lamina. Anterior foot-jaw not clawed, 

 posterior forming a prehensile hand. Inner branch of 

 first foot broad, 1 -jointed; fifth pair forming broad 

 laminar expansions; caudal segments broad and 

 laminated. 



The genus Porcellidium is the only representative of 

 this sub-family. 



