It leaves Bogra at the Chanda kona and flowing in a southerly direction past Raiganj and Shujapur is joined by the Ichhamati at Nalka.

The Phuljhur then flows south past the important village of Ullapara, a few miles below which it joins the Hurasagar at Narnia after a course of about 64 kilometres (40 mi) in this district.

After this junction, it takes the name of the Hurasagar and passing close by Shazadpur and Hera joins the Jamuna near Bera.

before the destructive floods of 1787 it brought down to the Atrai and to the Ganges a great volume of Teesta water.

Since the main stream of the Teesta was diverted to the east in 1787, the Karatoya and the Phuljhur have gradually silted up.

Traces of an old channel, for which the name of the Karatoya is claimed, are also pointed out in the Chatmohar thana, where it appears to have been obliterated by the Baral.