1. Trilobytes
   1. 3 lobes
      1. left
      2. central
      3. right
   2. cross-divisions
      1. headshield
         1. compound eyes
      2. trunk
         1. segments
      3. tailpiece
   3. shed shells
      1. broke into pieces
2. Crinoids
   1. calcite plates
   2. umbrella like arms
      1. tube feet
      2. pick up food particles
   3. avoided mud
      1. clogs them up
   4. animals, not plants
   5. rays with multiple arms
      1. pinnules on arms
         1. branches
3. Corals
   1. silurian corals
      1. rugose
         1. colonial
         2. solitary
         3. Summary
            1. skeleton shell
            2. corallite
            3. radial partitions
            4. septa
            5. parents
            6. split up
            7. asexual reproduction
      2. tabulate
         1. colonial
         2. smaller corallites
         3. smaller/absent septa
   2. modern corals
      1. scleractinian
         1. conspicuous septa
         2. aragonite skeleton
            1. not calcite
            2. dissolves
            3. less specimens
         3. generally warm, clear, shallow seas
         4. symbiotic relationship with algae
            1. photosynthesise
   3. likely that ancient corals lived in warm water
      1. palaeozoic & scleractinian unrelated
      2. no evidence for palaezoic corals and algae