Fig. 4
From: Non-invasive imaging techniques combined with morphometry: a case study from Spirula
Illustration of the ontogenetic development of the Spirula spirula shell. a Whorl interspace index (WII). b Umbilical width. c Umbilical width index (UWI). d Whorl expansion rate (WER). e Absolute septa index for a circle of 20-mm diameter (ASI20, filled circles) and Septa per demiwhorl (SDW, open circles). f Septal distance in angles. g Total rotational angles. h Chamber volumes. a–e With the diameter plotted on the x axis, f–h Chamber number plotted on the x axis