domina, and one with a portion of a leg, so early in the Ordovicic in muds derived from Appalachia is most suggestive. In the succeeding Schenectady beds in the same general region, in muds also washed down from Appalachia, occur a number of specimens which, in the shape of the carapace, position of the eyes, etc., suggest their generic reference to Stylonurus and have been described by Clarke and Ruedemann as S.? limbatus. They have furthermore found a number of body segments "which have the form and ornamentation of the Otisville species Stylonurus myops" (39, 296). Although it is a little out of chronological order to bring in the Utica species before taking up the Schenectady fauna, this, nevertheless, is the logical place for its discussion. Echinognathus clevelandi was described from a single endognathite which has shown two diagnostic characteristics, namely, an extreme spinosity, and a peculiar and distinctive type of surface sculpture. Clarke and Ruedemann state that this species "was either closely related to Stylonurus or had a convergent development to that genus as far as the two characters mentioned are concerned" (39, 322). It may quite properly be asked why it is that if the single endognathite known, shows only two diagnostic characteristics, and these two are recognized as definitive of Stylonurus, the species does not belong to that genus, or at least is it not more than likely, if more specimens are discovered, showing other parts of the body, they will be found to represent Stylonurus? It seems to the author that the geographical and geological position of E. clevelandi alone would suggest the greater possibility of the form being a Stylonurus. To be sure, this is somewhat speculative, but it is a suggestion for future work and consideration; it is sufficient that the Utica species is at least closely related to the genus Stylonurus which was found at earlier periods and also in the Siluric and Devonic, always in deposits derived from Appalachia. This statement includes the Utica beds just mentioned, for it is now recognized that, as Professor Grabau first pointed out, the muds were carried down from Appalachia and were merely the eastern near-shore facies which replaced that of the Trenton limestone facies (Grabau, 84, 231–232). Passing on to the next time in the history of North America when the genus Stylonurus is known to occur, we find S. (Ctenopterus) multispinosus in the Pittsford and two well defined species of this genus, as well as many fragments specifically indescribable though evidently distinct in the Shawangunk, both of which formations have been interpreted on stratigraphic grounds and on a comparison of the two faunas inter
