ABSTRACT
For many of the known conical flock planes, the full collineation group is also known. This means that using this group, we may determine how many mutually non-isomorphic Ostrom-derivates actually are produced per skeleton. We have shown that normally, there are at least two non-isomorphic Ostrom-derivates when the skeleton is transitive. Indeed, for the known transitive skeletons, such as arising from the Penttila flocks or the Adelaide flocks, there are an enormous number of ‘missing’ spreads that may be obtained by derivation of the base reguli.
