API/Modloader
Forge

Describe the bug
Bulbis shells and purple bulbis shells are solid blocks. This means that

• Entities can suffocate inside of them,
• They can conduct redstone signals,
• Mobs may be able to spawn on them, if a mod adds a mob that can spawn in the light level 11 the shell gives out,
• A chest can't be opened underneath them, and
• They are susceptible to other behaviours affected by opacity documented on the Minecraft wiki.

To Reproduce

• Point a powered repeater into the side of either bulbis shell, and place redstone dust on any other side. The dust becomes powered.
• Place a chest under either bulbis shell, and attempt to open it.
• Use spectator mode to clip your character's head into the shell, and enter survival mode. The character suffocates and then enters crawl mode.

Expected behavior
Because they are visually transparent, bulbis shells would behave like leaves, ice, glass, and so on, and not conduct redstone, suffocate mobs, etc.

Screenshots/Videos
A shell conducting redstone.