BUFFALO SOCIETY OF NATURAL SCIENCES . 217 



coming from rivers of different continents, but there may be single 

 cases of a family, a genus, or even a species which occurs in sediments 

 from one land mass, which is nearly related to or identical with one 

 in sediments coming from another land mass. In such a case, to de- 

 termine true relationships one must compare the whole of each fauna, 

 species by species, and must in addition study the ancestors of each 

 fauna and of each species in the preceding periods wherever possible. 



THE EURYPTERID FAUNAS CONSIDERED BY CONTINENTS 



The Eurypterid Faunas of Appalachia. Let us turn now to the 

 placing of the various pre-Siluric eurypterids. Strabops thacheri from 

 the Cambric is too primitive and morphologically undifferentiated to 

 be looked upon as more than an ancestral form approaching the pro- 

 totype and from which several branches of the eurypterid tree di- 

 verged. The first prolific eurypterid fauna in North America, the 

 first to offer sufficient material and a large enough representation in 

 genera and species to make it possible to state what are the general 

 affinities of the fauna as a whole, is the newly discovered one in the 

 Normanskill shales at Catskill, New York, which has so far been found 

 to contain six species, included in five genera, but undoubtedly many 

 more will be discovered as the material is worked over. On account 

 of the fragmentary nature of the abdomina found, and because the 

 carapaces are usually dissociated from the rest of the body, generic 

 determinations have been provisional and comparisons with related 

 species difficult. Yet the fauna shows a pronounced and altogether 

 surprising similarity to that of the Schenectady beds (Trenton) de- 

 spite the difference in. age. In the case of Pterygotus? (Eusarcus) 

 nasutus, Clarke and Ruedemann "have been unable to distinguish 

 the Schenectady and Normanskill types," (39, 412); and have re- 

 ferred a number of carapaces from the Normanskill beds to P. nasu- 

 tus, a species described originally from material from the Schenectady 

 shales. Eusarcus linguatus from the Normanskill is very similar to 

 Pterygotus} {Eusarcus) nasutus? Eurypterus chadwicki, Dolichop- 

 terus breviceps, and Stylonurus modestus are not well enough repre- 

 sented for relational comparisons to be made, so far as species are con- 

 cerned. The finding of several Stylonurus carapaces, attached ab- 



2 Clarke and Ruedemann point out this similarity, but claim also that E. linguatus "strongly 

 suggests the Eusarcus vaningeni" from the Salina, in position of eyes and shape of carapace (39 , 

 414). A close examination of their descriptions and of all the figures they give does not reveal any 

 marked similarity. 



