Lost property

There have been some wild nights at sea of late and numerous mermaids have lost their purses.  

I went to the beach to see if I could find any  Portuguese Men of War that have been spotted there following the recent.storms but there were none. Instead, the seaweedy debris on the strandline  was littered with these leathery sachets,  the egg cases of the nurse-hound, a sort of dogfish - alternatively,  confusingly, called  the cat shark. One of the pouches was still attached to a seaweed stem by its tangle of wiry tendrils  but the (single) eggs inside were either hatched or deceased.

It must have been a night to remember at the mermaids' ball.