se, but not for any phyletic reasons, as derivatives from Appalachia, the Pittsford constituting the upper part of the Shawangunk (see p. 101 above). The problematic form from the Portage sandstone referred to S.? wrightianus is too incomplete to be of much value. It probably belongs to Stylonurus; it certainly occurs in an otherwise unfossiliferous deposit which has been interpreted by Grabau as partly of river floodplain and partly of wind-blown perhaps loess-like origin (87, 553, 569). Finally, the Upper Devonic yields two species of Stylonurus: one, S. beecheri described from a single individual, none too complete, from the Chemung sandstones of Warren, Pennsylvania; the other S. (Ctenopterus) excelsior from two specimens from the Catskill beds of New York and Pennsylvania. This latter species is related in many respects to S. (Ctenopterus) cestrotus from the Shawangunk, both belonging to the same sub-genus. The Catskill is a continental deposit whose material as shown first by Grabau (86) and later by Barrell was derived from Appalachia. The specimens of S. excelsior were beyond a doubt washed out into the Chemung sea, since all of the species of Stylonurus so far known from North America came from Appalachia, as has just been demonstrated.
Having now followed the history of this one genus from Ordovicic through Devonic time and found that it always lived in the rivers of Appalachia, let us return to the genus Dolichopterus in the Normanskill beds, and trace its subsequent occurrences. As in the case of Stylonurus, the specific relations of the Normanskill form cannot be determined, for only a single small carapace is known, but the point of especial interest is the occurrence thus early of a Dolichopterus. This genus is represented by two species certainly, and one doubtfully, in the succeeding Schenectady beds. Two specimens described under the new species of D. latifrons by Clarke and Ruedemann agree "closely with D. otisius" from the Shawangunk in the posterior contraction of the carapace (39, 270). The carapaces and metastomes of D. frankfortensis (Schenectady) do not seem to show close relationship to other species of the genus, though one metastoma "has been found which recalls that of D. macrochirus" from the Bertie (39, 269). A few fragments having certain Dolichopterus and certain Eurypterus characteristics have been referred to E.? (Dolichopterus?) stellatus, but they are of no value in the present discussion. Thus it is seen that in the meagre, unsatisfactory material from the Normanskill representative of Dolichopterus, one species shows affinities to a Shawangunk form, and one specimen of a second species recalls char-
