Among the longer rivers are the Cree, which rises in Loch Moan and reaches the sea near Creetown after a course of about 30 miles , during which it forms the boundary, at first of Ayrshire and then of Wigtownshire; the Dee or Black Water of Dee (so named from the peat by which it is coloured), which rises in Loch Dee and after a course mainly S.E. and finally S., enters the sea at St Mary's Isle (actually a peninsula) below Kirkcudbright, its length being nearly 36 miles (58 km); the Urr, rising in Loch Urr on the Dumfriesshire border, falls into the sea a few miles south of Dalbeattie 27 miles (43 km) from its source; the Ken, rising on the confines of Ayrshire, flows mainly in a southerly direction and joins the Dee at the southern end of Loch Ken after a course of 24 miles (39 km) through lovely scenery; and the Deugh which, rising on the northern flank of the Windy Standard, pursues an extraordinarily winding course of 20 miles (32 km) before reaching the Ken.