Ted Trueblood's Otter Shrimp is a classic nymph designed to be fished as a scud and was originally dubbed with a blend of otter and cream seal fur.
Angora goat or a cream colored synthetic are the modern substitutes for the seal fur.
The tail and legs were tan partridge.
The original was dubbed much thinner than in the picture above.

Ted Trueblood was the fishing editor for Field and Stream in the 40's and 50's. He designed the Otter Shrimp to be the right color and translucency but without other specific details that would alert the trout to a fraud.
His intent was a fly that suggests food rather than imitates it