222 PALAEONTOLOGY OF NEW YORK. 



tapering rapidly, and was undoubtedly divided into several joints although the 

 articulating surfaces cannot be detected. Along the lower margin of the 

 appendage is a double scries of strong spinous processes, each having a length 

 of about 25 mm. Four of these and the bases of two others constitute the 

 outer row. and portions of two members of the lower row are partially ex- 

 posed. The terminal spine is incurved toward the tip, and all are characterized 

 by the longitudinal elevated lines upon their surface. A fragment of the basal 

 joint of the left leg of the same pair lies in its normal position, and a small 

 portion of its mandibular process is exposed. 



The carapace has been so forcibly compressed upon the basal joints of both 

 these appendages as to produce conspicuous ridges upon the surface equidistant 

 from the anterior prolongation of the median ridge of the cephalon. 



Directly behind the base of the right member of this pair lies a single joint 

 terminating in a chela, the whole measuring 60 mm. in length. The other 

 joints of this appendage do not appear on the specimen, and it is impossible to 

 determine positively whether this is. as it seems, the terminal portion of a third 

 gnathopod, or is analogous to the chelate antennules of Limulus. 



A portion of a very strong basal joint, belonging to the left member of the 

 third pair of appendages, has a diameter of 30 mm., a length of 35 mm., and 

 bears a double lamellate mandibular extension, which is sharply serrate along 

 its oral edge. This joint is followed by a small portion of a fourth gnathopod, 

 which has a diameter of 40 mm., and though quite imperfect represents a very 

 large appendage. Behind this, and lying in its normal position is the basal joint 

 of the last or fifth pair of appendages. This is very broad and fiat, as in other 

 members of the Eurypterida, has a length of 90 mm., a width of 60 mm., and 

 a thickness of 20 mm. at its distal extremity. The oral margin of the joint 

 bears a row of conspicuous denticulations. 



According to the restoration of Stylonurus Logani given by Woodward (Mon. 

 Brit. Toss. Merostomata, pt. iv, p. 131), the last two pairs of gnathopods were 

 produced to a length nearly equaling that of the entire body. This may be 

 true also of Stylonurus excelsior, and as the specimen under consideration bears 

 the largesl carapace of Stylonurus at present known to us, these appendages 

 may have reached a length of upward of four feet. 



The evidence from this specimen confirms in most particulars Woodward's 

 restoration of the oral surface of Stylonurus, though there is reason to believe 

 that the peculiar antennae there ascribed to the animal represent the first pair 

 of gnathopods, and that there were five instead of four pairs of these append- 

 ages as given by the author. 



