Hello. These are most likely phosphatic nodules, which are common in the basement bed of the Red Crag. They used to be quarried for grinding into fertiliser in SE Suffolk the 1870s and are known as 'coprolites’. They have a fine-grained interiors and their exterior has a polished look. They are not true coprolites (fossil dung), but a kind of highly phosphatic mudstone (phosphorite) concretion, rolled and smoothed by marine action.