396 CRUSTACEA [Octobci^ 



attenuated towards the base, terminal segment of the 

 latter large, membranaceous, nearly as long as the seven 

 preceding ones conjunctly, dilated at the base and gra- 

 dually attenuated towards a point at tip, with a percepti. 

 ble longitudinal line on the middle; lateral styles mem» 

 branaceous, almost filiform, longer than the peduncles 

 and much shorter than the terminal segment of the tail; 

 f€et gradually longer to the seventh pair, which are much 

 lunger than the others. 



Length nearly two inches. 

 Belongs to the genus Mga of Dr. Leach. 

 It seems probable that this species resembles the 

 Gaudeloupensis, but is larger; it is very commonly found 

 in the mouths of the mossbankers^ (C. tyrannus) as above 

 mentioned; the body is generally more or less contorted, 

 in compliance with the form of the part of the mouth to 

 which it was attached. An interesting account of this 

 species is given by Mr, Latrobe under the name which I ' 

 have, of course, adopted; the lateral lamellae of the tail, 

 which he supposed to be single, are in reality bifid as 

 in the other species of this genus. I had an opportunity 

 to examine a number of these fish, and of them, many- 

 were infested with this animal, but by no means every 

 one, as has been supposed. The fishermen say the Fish' 

 louse is necessary to the life of the fish, and as a proof 

 of it, they observe that if the louse be taken from him 

 the fish will die, although thrown into the water; but it is 

 probable that the death of the fish is not owing to the re- 

 moval of the parasite, but its to being withheld too long 

 from the water, as it is well known that this fish lives but 

 a very short time when taken from the water. 



