tectorium

Fusulinidae with flat or slightly fluted septa, wall of three or four layers including diaphanotheca and generally pronounced outer tectorium.

The Romans distinguished three principal kinds of atramentum, one called librarium (or scriptorium), another called sutorium, the third tectorium.

Early Fusulinidae from the Upper Carboniferous (Moscovian), commonly with only three or four whorls, thin and weakly differentiated walls, inconsistent outer tectorium, prominent axial fillings and a possibility of chomata.

Atramentum librarium was the writing ink of Roman times, atramentum sutorium was used by shoemakers for dyeing leather, atramentum tectorium (or pidorium) was used by painters for some purposes, apparently as a sort of varnish.