Page:The Habitat of the Eurypterida.djvu/232

representative of the genus" (p. 342). Thus the nearest affinities of this Schenectady species are to forms from the Pittsford and Shawangunk, which it has been suggested might themselves be merely growth stages and not "species." Only comparatively young (for the most part nepionic or neanic) individuals are known from the Shawangunk, but it is significant that many of these are almost identical in

Fig. 19a. Eusarcus triangulatus. Clarke and Ruedemann. ✕ ${\tfrac {1}{2}}$.
(After Cl. & R. 1912, pl. LXXXIV, fig. 7)
Fig. 19b. Eusarcus scorpionis. Grote and Pitt. ✕ ${\tfrac {1}{2}}$.
(Outline after Cl. & R. 1912, pl. XXVII, fig. 1, restoration)

form of the carapace and the position of the eyes with larger, neanic or ephebic individuals from the Schenectady, indicating relationship by this recapitulation of characteristics in ontogeny (see fig. 20.) The two remaining species of the Schenectady fauna, Pterygotus (Eusarcus?) nasutus and P. prolificus are unlike any other species known from this country, so that their comparative value is small. Although

Fig. 20a. Hughmilleria shawangunk Clarke. Nepionic Individual. ✕ 8.
(After Cl. & R. 1912, pl. LXIV, fig. 2)
Fig. 20b. Hughmilleria magna. Clarke and Ruedemann. ✕ ${\tfrac {1}{2}}$.
(After Cl. & R. 1912, pl. LXXXV, fig. 11)

the last mentioned species is the most profuse in the Schenectady beds, yet the variability in the shape of the carapaces is so great that one might easily be led astray in drawing conclusions. On the whole, the study of this fauna reveals it to be rather unsatisfactory. For one thing, it is made up for the most part only of carapaces and these are often fragmentary; besides, the forms are so distinctive, possessing such unique and specialized characteristics, that with our present