CALIGUS. 313 



Gen. 172. CALIGUS, Matter. 



Thorax of only two distinct joints. Frontal plates with a 

 small sucking-disc on the under surface of each side. Fourth 

 pair of feet slender, of one branch, and used for walking. 



Caligus diaphanus, Nordmann. — The male has the cara- 

 pace large, and nearly round ; thorax much smaller than 

 carapace. 



Hab. On the turbot, gurnard, mackerel, coal-fish, cod- 

 fish, and others, in Belfast Bay, 



Caligus rapax, M. Edw. — The female has the carapace 

 oval, much longer than broad ; frontal plates large and 

 nearly straight in the centre ; antennae very large. The male 

 rather smaller than female, and has the last joint of thorax 

 smaller ; the abdomen is longer and narrower. 



Hab. Belfast Bay : on the gurnard, John Dory, whiting, 

 and other fishes. 



Caligus Mulleri, Leach. — In the female the carapace 

 is oval, rather longer than broad ; the frontal plates large, 

 notched in the centre. Antennas with basal joint large. 

 Abdomen very short and rounded. In the male the last 

 joint of thorax is smaller and more rounded. 



Hab. On cod and brill. 



