Page:The Habitat of the Eurypterida.djvu/231

Rh From the great mass of detail which it has been necessary to give, we are at length able to reach two conclusions: (1) Stylonurus from its earliest appearance in the Normanskill beds (Black River or Basal Trenton) to its last appearance in the Chemung was an inhabitant of the rivers of Appalachia; (2) Dolichopterus also first known in the Normanskill, but so far not known from beds later than the Bertie, is most rationally to be considered as restricted in its habitat to the rivers of Appalachia, although the paucity and the condition of the specimens make this conclusion not absolutely certain.

This much being determined, we may consider the remaining faunas which have been found in sediments which from other lines of reasoning are recognized as coming from Appalachia. In the Schenectady shales eleven species are recorded, of which four have already been discussed. Of the remaining seven, Eurypterus ruedemanni and E. pristinus are represented each by a single carapace neither of which is of use in comparisons, and the same may be said of the doubtfully determined form Euscarcus (?) longiceps of which a few incomplete carapaces are known. Nine carapaces of Eusarcus triangulatus have been found, and these Clarke and Ruedemann state "have in common the broad, short, subtriangular form; and the forward position of the marginal lateral eyes bears a close resemblance to the carapace of E. scorpionis from the Bertie waterlime" (39, 258). Yet the figures, measurements and descriptions of these two species given by the above mentioned authors do not bear out this "close resemblance." In reference to E. triangulatus they say that the carapace is "twice as broad as long (length of type, 20 mm., width 43 mm.)" and of E. scorpionis they say that the carapace is about "as broad as long" (p. 234), while in the measurements which they give of this species the length is to the width (in millimeters) as 18:22, 60:66, and 56:59, respectively. For comparison I give outline drawings of the restoration of the carapace of E. scorpionis and of the actual carapace of the type of E. triangulatus (Figs. 19a and b). One of the commonest species in the Schenectady shales is Hughmilleria magna, known from a number of carapaces, some abdomina, and a half complete individual. "This exhibits a form of the preabdomen corresponding to H. socialis," but the swimming leg is "relatively longer than that of H. socialis" (Pittsford) (39, 342). Several detached body rings have been found regarding which Clarke and Ruedemann say: they "exhibit a type of ornamentation, consisting of transverse lines near the anterior margin, known to us only in H. shawangunk, the Otisville