Just struck me funny about attachments so maybe I can make up for it.
First off the xenophora are reportedly very choosey about what they attach
and once the object is decided on, take up to 2 hours to position and clean
both object and shell. Then it can take up to 10 hours for drying, at
different times there can be a rocking motion to check position and amount
of glue. For individual species some do appear to have tendencies. Normally
you can tell where a conchyliophora comes from by its attachments, it could
be one of 5 different places. Corrugata usually attach large object that are
close to each other on the peripheral edge. Granulose evenly spaces the
attachments on the peripheral edge. Flindersi usually have a small pebbles
in-between larger ones. So yes there are some species that have tendencies
but don't book on it. I have found every time I think I understand xenophora
one comes along and throws a monkey wrench in to it. Most about xenopohra is
guess-a-latting. I would love to know their breeding cycle, why some stop
attaching, a chemical change? Maybe we will never know until a chimera is
placed among them or some one has the felicities to do a down and dirty
study. Until then, they are a fascinating family that keeps you shaking your
head.
Hope this answers some questions,

Harry