Excerpt from A Monograph of the Naiades of Pennsylvania, Vol. 3: Systematic Account of the Genera and Species
With regard to the systematic literature, I have refrained from giving a full list of references and synonyms under each species, since the citations given by Simpson (1914) are as complete as could be desired. The quotation of the earlier reports from Pennsylvania was deemed desirable, in order to get an idea of the advance made in recent years in our knowledge of the subject.
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