42 



length, 2% inches. A fragment of the first and second joint attached 

 to it show that the scale-like facets become a smaller and of more 

 equal size as they pass from the first to the second joint. The little 

 elevated dentate band near the margin of each joint, which is so 

 characteristic of E. pachycheirus, is also present in this species. 

 Found in the water-lime group near Buffalo. 



2. Pterygotus globicaudatus, n. sp. (Plate II., Fig. 2.) 



Only one specimen has been found, consisting of five abdomi- 

 nal segments and tail. The segments are coarse and all of the same 

 length, \% inches; they increase rapidly in width, from 2^ inches 

 for the posterior segment to 5X inches for the anterior one and form 

 strong, angular, lateral extensions over each other; the lateral mar- 

 gins of the joints are finely serrated in their posterior parts. The 

 markings on the largest segment consist of scales overlaying each 

 other. These scales are very small and delicate at the anterior por- 

 tion and increase rapidly in size as they approach the middle and the 

 posterior portion of the segment. In the remaining four segments 

 the surface markings consist of large, irregularly-shaped and irregu- 

 larly distributed pustules. The tail is fiat, 2V& inches wide and xV& 

 inches long, oval in shape, and has its lateral margins regularly ser- 

 rated; the posterior margin is smooth, and represents an even curve. 

 The anterior margin in its connection with the last segment of the 

 body, is 1% inches wide. The surface markings are of the same 

 pustulose character as those on the four abdominal segments. 



Although the tail of this Pterygotus can be considered as flat, 

 compared with the tail of the Eurypteri its shape in life must have 

 been spherical, and corresponding with- the body in thickness, for 

 the caudal appendage of this specimen measures in its middle por- 

 tions, three-eighths of an inch between the dorsal and the ventral 

 surfaces, while the bodies of the Eurypteri in their thickest parts 

 rarely exceed one-quarter of an inch. 



Length of specimen, 8 inches; greatest width, 5X inches. 

 Found in the water-lime group near Buffalo. 



3. Pterygotus acuticaudatus, n. sp. (Plate II., Fig. 3.) 



The tail of this species is longer than the two last abdominal 

 segments combined, whereas in P. globicaudatus it is comparatively 

 shorter, but wider. The specimen shows the tail with a length of 



