These layers, produced by accretionary growth
, can be used to estimate the age of P.
The microconchids are essentially hollow calcareous tubes showing evidence of accretionary growth
In larger specimens, the shell may reach over 6 cm in length (Hunt, 1877), and shows accretionary growth
bands analogous to those seen on the shelves of bivalves or other molluscs (e.g., Fig.
In other words, while the animal survival success may partially depend upon the (presumably) functionally relevant set of shell-shape parameters [9-29], the animal control upon this category of shell-shape parameters is only indirect, readily operating only via the accretionary growth
process of shell, which is best accounted for by the set of growth-based shape parameters (defined below).
This is because the shape of shell outline is not a geometrical figuration generated per se, defined at the outset, but it is the cumulative result of an accretionary growth