Land and Fresh-Water Crustacea around Edinburgh. 77 
Edward; it is also recorded from a few places in England, 
but I have not seen it. It may be easily overlooked owing 
to its colour and small size, and by mistaking it for the 
young of a common and larger species. Platyarthrus is 
worth seeking for, because of its interesting habitat. I do 
not know whether it restricts its association to a particular 
species of ant or not. It would be interesting to find out 
if this were so, as well as the reason why it takes up its 
abode in ants’ nests, a habit so different from its confreres. 
Bate and Westwood record finding it “in the nests of the 
common brown garden ant at Hammersmith.” 
Oniscus asellus, Linné. 
1741. Oniscus asellus, Linné, Systema Nature, ii., p. 1061. 
1868. © » Bate and Westwood, loc. cit., ii., p. 468. 
Habitat.——Under stones, leaves, old wood, about old walks, 
etc, common and generally distributed. Oniscus has the 
anterior antenne eight-jointed, and thus differs from the 
next genus, Porcellio, which has seven-jointed antenne. 
O. asellus is one of our most common Isopods, being found 
almost everywhere. Its colour is a prettily mottled slaty- 
blue and white, arranged in a biserial pattern from head to 
tail. Another species, O. fossor (Koch), is recorded from 
Banff by Thomas Edward. It is said to resemble 0. asellus 
very closely, and to be distinguished chiefly by its colour, 
which is “ of a more uniform brownish-grey,” but “exhibiting 
the same kind of pale patches and rows of spots seen in 
O. asellus.” It is said also to be more active than O. asellus. 
It is quite possible that O. fossor may yet be found in our 
district if carefully sought for. 
Porcellio scaber, Latreille. 
1802. Porcellio scaber, Latreille, Hist. Nat. Crust. et Ins., vii., p. 45. 
2 »,  dilatatus, Brandt and Ratzeburg, Arzne-Thiere, t. 12, 
' fig. 6. 
»,  dubius and affinis, Koch, in Cont. Panz., Heft 180, 
M. 8, and 13. 
1868. by scaber, Bate and Westwood, loc, cit., ii., p. 475. - 
Oniscus, 
Linné. 
Porcellio, 
Latreille, 
