30 



ular spine with serrated edges," and " eyes reniform or oval, placed 

 within the margin of the carapace." 



The species is well named, as the whole shape bears a striking 

 resemblance to that of a scorpion. Hereafter Eusarcus scor- 

 pionis should be known as 



EURYPTERUS SCORPIONIS, Grote and Pitt. 



Carapace almost straight in front ; broadly rounded at the 

 lateral anterior angles ; sides slightly curved for about two- 

 thirds of the length of the carapace, at which part it attains its 

 greatest width. The remaining posterior third of the lateral 

 margin in a slight curve decreases the posterior width of the 

 carapace a trifle; the posterior margin has a slight curve inwardly 

 in its middle third, and forms almost right angles with the lateral 

 margin. The length and width of the carapace are in propor- 

 tion as five to seven. The eyes are not very well defined in my 

 specimens, but seem to be semi-oval; they are larger than in any 

 other species of Eurypterus, and are placed near the margin of 

 the carapace in the broadly rounded anterior lateral angles. The 

 distance from the margin is less than the width of the eyes 

 themselves. (Fig. 3, Plate 3.) There are no surface markings on 

 the carapace. 



The first seven segments of the body form a large ellipse, of 

 which the fourth is widest, and the seventh contracts very remark- 

 ably, so that the eighth is only about one-fifth as wide as the 

 fourth. The ninth, tenth, eleventh and twelfth segments are only 

 a trifle narrower than the eighth, but increase in length poste- 

 riorly, so that the twelfth is nearly twice as long as wide. Indeed, 

 the four posterior segments are as long as the eight others 

 together. The surface of the specimen is very distinctly marked 

 with small triangular pustules, distributed very irregularly. 



The tail spine has a slight curve, which is a distinct character- 

 istic of the species, as all other Eurypteri have a straight caudal 

 appendage. It is about one-third longer than the posterior seg- 

 ment. 



The feet in all the specimens are not complete enough to admit 

 of any detailed description. 



