Page:Second Geological Survey of Pennsylvania Report of Progress PPP.djvu/15



The literature upon the subject of the palæozoic phyllopods is comparatively very meager and fragmentary. An occasional discovery of a few specimens, as in the present instance, has resulted in the publication of one or more new forms, but nothing has led to a compilation and review of the palæozoic forms of the whole order. The trilobita forming the bulk of palæozoic crustacea, and including such varied forms and numerous species, have received much attention from palæontologists, so that a nearly complete monograph of this order is now possible; while of the American ostracoda, merostomata, and phyllopoda, but little is yet known which would furnish materials for an exhaustive monograph of the fossil species.

In the present paper several new forms are presented and considerable structural detail is here first given for the genus, Whitfield}}, which it is hoped will add to our knowledge of the zoölogical relations of this and allied genera.

1839.—The first palæozoic fossils of this order were found in England and published by Sir R. Murchison. Professor L. Agassiz considered them as fin-spines of fishes, and