224 THE HABITAT OF THE EURYPTERIDA 



representative of the genus" (p. 342). Thus the nearest affinities of 

 this Schenectady species are to forms from the Pittsford and Shawan- 

 gunk, 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 Shawan- 

 gunk, but it is significant that many of these are almost identical in 



Fig. 19A. Eusarcus triangulatus. Clarke and Ruedemann. X %. 

 (After CI. & R. 191 2, pi. LXXXIY, fig. 7) 

 Fig. 19B. Eusarcus scorpionis. Grote and Pitt. X i- 

 (Outline after CI. & R. 191 2, pi. 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 {Eu- 

 sarcus}) 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. X 8. 



(After CI. & R. 191 2, pi. LXIV, fig. 2) 



Fig. 20B. Hughmilleria magna Clarke and Ruedemann. X 5. 



(After CI. & R. 191 2, pi. 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, possess- 

 ing such unique and specialized characteristics, that with our present 



