The later added " Williamsoceras ", " Cacheoceras ", and " Perkinsoceras " are true endocerids as indicated by their cylindroid shells, phragmocones, and siphuncles . " Williamsoceras " and " Cacheoceras " are from the Whiterockian stage ( lower lower Middle Ordovian ) of Utah . " Perkinsoceras ", which appeared somewhat later, is from the Chazyan of New York, like " Allotrioceras " and " Mirabilioceras " but rather distinct from either.
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