Abstract

A careful restudy has been made of the types of Climacograptus innotatus var. pacificus Ruedemann from the topmost Ordovician of western North America and of topotype material of Climacograptus innotatus Nicholson from the Lower Silurian of Scotland. The study shows that these two forms are morphologically unrelated, the former being represented by short, stubby individuals with complex spinose growths, including double genicular spines, and the latter by slender, lanceolate individuals apparently provided with genicular flanges. Var. pacificus is here recognized as a distinct species, Climacograptus pacificus, and typifies and is restricted to Late Ordovician graptolite faunas of western North America and the Pacific Faunal Province.A deformed individual from Idaho characterized by three or four genicular spines is distinguished as Climacograptus pacificus pilosus, subspec. nov.

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