1 Dorsal papillae not visible; sediment particles fused into crusts, covering papillae completely............ group “crustosa”
- Dorsal papillae visible; sediment particles, if any, not completely covering papillae................................. 2
2(1) Dorsal papillae without sediment cover, or sediment forming very thin layers; papillae tiny or forming tubercles..................................................................................................... group “ nuda ”
- Dorsal papillae with sediment cover, at least basally; tubercles present or absent.................................... 3
3(2) Body papillae small, often with long tip.........................................................group “ villosa ”
- Body papillae large, often transformed into tubercles, all of similar size, or in two markedly different sizes. group “ verrucosa ”