WATERLIME GROUP. 413* 



swimming foot. On another specimen, from the same locality, is a swimming foot 

 preserving the fonrth, fifth, sixth, seventh and eighth joints, with the terminal pa- 

 lette. The peculiar arching of the seventh [sixth] joint, and the thickened or inflated 

 character of the swimming foot in this species, appear to be sufiiciently characteri- 

 stic to rely upon for specific distinction. The joints of the thorax and abdomen have 

 the scaly surface marking more strongly developed than any other species observed; 

 and the anterior margin of each joint, which is imbricated by the one before it, is 

 raised in a little elevated band, more prominent and more strongly serrate on its 

 posterior edge than any of the other species. The surface is likewise marked by 

 strong longitudinal wrinkles somewhat irregularly disposed. The last four joints are 

 marked by a double row of scale-like pustules, as in other species. 



Fig. 1. The body of an individual of this species, preserving eight or nine articulations of 

 the thorax and abdomen. The surface is strongly marked by the scale-like facets, 

 and the articulations are coarse and strong. 



Fig. 1 a. A portion of the crust enlarged, showing the surface markings. 



Fig. 2. A fragment of stone upon which are preserved two swimming feet, the anchjlosed 

 ventral thoracic segment, and some portions of the anterior feet. These appear 

 to be the remains of a large individual, which has been broken up, and the parts 

 separated. The swimming foot 2 a shows the lower side, and the joints are par- 

 tially separated ; and fig. 2 6 shows the lower side of the other foot, also in a 

 reversed position. 



Fig. 2 c is the fragment of one of the anterior feet, and fig. 2 d is the same placed in a 

 natural position : the length of the spines is a very characteristic feature. 



Fig. 2 « is the anchylosed first and second segments on the ventral side, preserving the 

 thoracic appendage. The specimen is worn, and the line of suture is scarcely 

 perceptible. 



Fig. 3. A separate swimming foot, preserving the five outer joints. 



Geological position and locality. In the Waterlime group at Blackrock, and four 

 miles east of Buffalo. 



Eurjpteras pastulosas ( n. s.). 



Plate LXXXIII B. Fig. 1. 



Carapace very wide, somewhat semicircular, broadly rounded in front, 

 with posterior angles rounded and a little extended laterally. Eyes 

 broad reniform, distant from each other, and almost equidistant from 

 the lateral and anterior margins. 



SuBFACE pustulose ; the pustules of very variable size, and sometimes 

 assuming a scale-like form. Crust comparatively thick. 



