B indicates bones of pelvis and thigh.
The suborder Mysticeti includes the baleen whales, such as right whales, blue whales, and humpback whales. These whales lack teeth, and instead have a curtain of baleen hanging down from their upper jaw. Baleen is a hair or horn-like substance which forms a sieve which is used to filter water. Baleen whales are known for their long wailing songs which carry hundreds of miles. They include the largest animal ever living on earth, the blue whale.