Those of the south aisle are Perpendicular, with segmented heads.
Any one of them might be the unsegmented gut of the segmented animal.
A harvestman, for instance, lacks the waist, and its abdomen is segmented.
There is, however, an important advance on the segmented worms.
The pectoral fins are without the segmented axis of the archipterygium.
The mouth parts, which ...