Since it is conceded that the law of priority is invariable in its application to zoological nomenclature, it remains for us to apply it to the determination of our Butterflies. That some inconveniences may arise from the corection of errors, does not militate against our desire to be right. The question is, are Mr. Scudder's genera well founded, or, are his names entitled to precedence, not is it convenient for us to use them. without as yet entering an extended discussion upon the structural characters of our Butterflies, we will briefly notice Mr. Scudder's genera.