septulum

plural septula

1. anatomyA little septum; a division between small cavities or parts.

   1 more example

   Test small, elongate, subfusiform, with bluntly rounded poles, septa thin and widely spaced, thin and short transverse septula alternating with foramina, thickened at the lower ends where they join with the tops of the parachomata, one or two axial septula between adjacent septa, outer whorls may also have a secondary transverse septulum between adjacent primary transverse septula;

   2015, Alfred R. Loeblich Jr., Helen Tappan, Foraminiferal Genera and Their Classification, page 739

2. geographyA small partition or division within a rock or mineral structure, especially within the fossil of a foraminifera or similar microorganism.