29 



The ventral margins of the two posterior segments are sharply- 

 defined, but those of the anterior three are blurred and indis- 

 tinct, and have the appearance of a possible attachment of 

 appendages. Part of one foot is visible, resembling closely the 

 swimming feet of the Eurypteri ; it is partially covered by the 

 carapace, and consists of a large ovate shaped joint, whose equal 

 margins terminate exteriorly in an indentation, which holds a 

 small terminal palette similar to that of the Eurypteri. 



The caudal appendage consists of three spines, a large one in 

 the middle and a smaller one on each side. The largest is two 

 inches long and about 3-8 inch wide at its base, tapering from 

 here into a sharp point. It seems that this large spine was 

 triangular in shape and grooved or hollowed on its ventral side 

 for the reception of the two smaller ones, which appear as if 

 they had been hinged to the posterior margin of the fifth seg- 

 ment underneath and on each side of the large spine by a small 

 rounded articulation. 



The two smaller spines are 1 3-8 inches long ; they are widest, 

 3-16 inch, at about one-third from their anterior end. From this 

 widest part they taper to a sharp point posteriorly, and curve 

 down to a blunt rounded margin anteriorly, which portion is 

 partially covered by the large spine. The posterior part of the 

 latter is delicately striated longitudinally. The two smaller 

 spines are without markings. 



Length of the whole specimen 8 1-2 inches, length of carapace 

 3 1-2 inches, greatest width of carapace, 1 7-8 inches. 



Found in the Waterlime group near Buffalo, N. Y , and pre- 

 sented to the museum by Mr. Herbert U. Williams of this city. 

 • EUSARCUS, Grote and Pitt. 



This genus was established, (B. B. S. N. S., Vol. iii., pp. 1-2,) 

 upon a specimen without tail and a partially broken carapace. 

 Since that time I have found several specimens, more or less 

 complete, which show that a new genus is not admissible here, 

 and that it must be classed with the' Eurypteri, because the lead- 

 ing characteristics of the genus, as given by Dekay, are present, 

 "a terminal joint prolonged into a sublinearor lanceolate triang- 



