NIAGARA FALLS AND VICINITY 23 1 



Eusarcus scorpionis Grote & Pitt {Buffalo soc. nat. sci. Bui. 3:1) 

 Distinguishing characters. Smaller than the foregoing; average 



length about i foot. Appearance strikingly scorpioid. Telson 



strongly curved. 



In the Waterlime at North Buffalo. 



Genus pterygotus Agassiz 



[Ety. : -Tefju)'wr6<^ , winged] 



(1839. ]\'Iurchison. Silurian system, p. 605) 



Large, often gigantic eurypterids, with a semiovate cephalothorax, 

 anterior marginal eyes and central ocelli. The first pair of cephalo- 

 thoracic legs (pre-oral) very long, slender, terminating in large pin- 

 cers or chelae, and probably prehensile in function. Behind the 

 mouth are four pairs of slender walking legs, and behind these are 

 the large swimming feet, which differ from those of Eurypterus 

 in being less broadly expanded at the ends. Telson an oval plate, 

 either terminating in a short projecting point or bilobed. 



Pterygotus macrophthalmus Hall (1859. Pal. AL Y. 3:418'^), 

 Pterygotus buffaloensis Pohlman (Buffalo soc. nat. sci. 

 Bui. 4:17) and Pterygotus acuticaudatus Pohlman 

 (Buffalo soc. nat. sci. Bui. 4:42) 



Distinguishing characters. Cephalothorax subquadrate or taper- 

 ing anteriorly; eyes very large and high^ with circular base. Chelae 

 (pincers) with angular front end ; posterior denticles on larger ramus 

 inclined and serrate. 



In the Waterlime at North Buffalo. 



Pterygotus cobbi Hall (1859. ^<^^- ^- ^- 3•4I7'^ pl- 83B, fig. 4), 

 Pterygotus c u m m i n g s i Grote & Pitt (Buffalo soc. nat. sci. 

 Bui. 4:18) 



Distinguishing characters. Animal large; chelae (pincers) with 

 curved front ends and erect non-serrate denticles. 



Rare in the Waterlime at North Buffalo. 



Pterygotus globicaudatus Pohlman (Buffalo soc. nat. sci. Bid. 4:42) 

 Distinguishing characters. Animal rather small; surface coarsely 

 tubercled; telson circular without median keel. 



A single specimen from the Waterlime of North Buffalo. 



