The Burgess shale, in particular, contains the fossils of all sorts of worms, arthropods, sponges, etc. The way they are positioned in the rock indicates that they were caught in an underea mudslide.
There are no fish bones, scales, teeth, or any other indications of fish.
Why?
Why is this true in all lower and middle Cambrian formations?
Why are fish found in all later marine formations?
In fact, in the Burgess shale, there are no indications of any vertebtrate animal. No fish, no whales, no sea snakes, no sea turtles, no birds, no otters, nothing.
The Burgess shale apears to be localized and has hardly been exhausted as to its content. Why should one necessarily expect to find fossilized fish in this location unless he assumes this formation took place over a long period of time and demonstrates a history of life forms from the simple to the more complex?