288 AGIDA. 
the other sex a smaller specimen (1? inch long), having 
the two basal joints of the upper antennz not dispro- 
portionably enlarged, and the last large segment of the 
tail emarginate-truncate, with a shallow furrow down the 
centre, and two obtuse raised keels at its sides. In other 
respects no difference appeared to exist. Except that 
the eyes in the figure of this smaller individual are 
represented as being of the same size as in the larger 
ones (uniting in the centre of the forehead), we should 
have referred it to Dr. Leach’s Aga bicarinata, or more 
probably to 4. tridens, with the central tooth of the tail 
plate worn away (the eyes being large, as in that species). 
Dr. Johnston, however, regarded it as belonging to the 
same species as the larger individuals, and probably the 
male of it, considering the dilatation of the basal joints 
of the upper antennze as a sexual character, or one de- 
pendent on age (and of insufficient value, therefore, to 
be ranked among the characters which are seized upon 
to divide tribes and families from each other), and also 
that the conformation of the terminal segment of the 
tail is not sufficient to discriminate species, as Dr. Leach 
seems to have believed, ‘‘ for his specific characters em- 
brace no other part,” at least in the species of Aiga. 
Unfortunately the comparative rarity of these parasites 
does not yet allow us to determine this point. 
The individual of this species described by our late 
friend Dr. George Johnston was taken in Berwick Bay 
on a cod-fish, and is preserved in the British Museum, 
which also contains another specimen from the Northum- 
berland coast, presented by Mr. R. House. 
There are also British specimens of unnoticed locality in 
the Hopeian collection ; and we have received them from 
Shetland, from the Rev. A. M. Norman, who alse records 
it from the Moray Frith. 
