152 MR MALCOLM LAURIE ON SOME EURYPTERID REMAINS FROM THE 



oar-like jaw-feet, instead of the single pair of broad, short, natatory organs more usually 

 met with in this group,"' 5 " is represented by two species, both hitherto unknown to 

 science. 



■ Stylonurus ornatus, n. sp. (PI. I. figs. 1-8.) 



This species is represented by fragments of three or four specimens which leave much 

 to be yet ascertained as regards the exact proportions. 



The carapace, of which only the ventral surface is shown, is horseshoe-shaped, with 

 a somewhat straight front margin. At its broadest point, which is about one-third of its 

 length from the front end, it measures 150 mm., while at its posterior margin the breadth 

 is only about 90 mm. In length it was probably about 150 mm. The anterior edge is 

 bounded by a border 7 mm. in width, marked by 3 equidistant parallel lines. This border 

 diminishes in breadth down the sides, and finally disappears about halfway down. Inside 

 this border lies the inturned portion of the carapace, broad in front (32 mm.), but, like 

 the border, narrowing down the sides, and disappearing close to the posterior edge of the 

 carapace. A pair of curved lines run one on each side about 15 mm. from, and nearly 

 parallel to, the margin of the carapace, approximating slightly to it along the anterior 

 border. These lines approach to within 20 mm. of each other in front, and then bend 

 abruptly, and run in a posterior direction to near the margin of the inturned portion. 

 While the border appears to be free from any surface sculpture, this is far from being the 

 case with the inturned portion. Down the sides where they are best shown, the sculp- 

 ture consists of very fine scale-markings (fig. 3), with the convex side turned outwards 

 towards the margin of the carapace. These markings do not extend to either boundary 

 of the inturned portion, as they disappear some little way from the margin of the cara- 

 pace towards the outer side, and towards the inner side are replaced by fine anastomosing 

 lines, more or less longitudinal in direction. Within the inturned portion of the carapace 

 the central space is occupied by the bases of the legs, but these are unfortunately not 

 clearly enough shown to be accurately described. 



The eyes can be made out lying just within the inner margin of the inturned portion 

 of the carapace, 34 mm. from the anterior margin, and about 31 mm. from the side. They 

 appear to have been oval in form, the major axis, which lies at an angle of 45° to the 

 axis of the body, measuring 18 mm. and the minor 10 mm. This is small in proportion 

 compared with the eyes of some of the other members of the genus. 



The first six (mesosomatic) free segments are partly seen in fig. 1. Owing to less 

 than half the segments being preserved, it is impossible to determine their width in this 

 specimen. The length of the respective segments is as follows : — 1st, 16 mm. ; 2nd, 

 18 mm. ; 3rd, 21 mm. ; 4th, 23 mm. ; 5th, 23 mm. ; 6th, 18 mm. The 5th segment thus 

 shows no increase, and the sixth a slight diminution in length. The posterior margin of 

 each segment in this specimen, which shows the ventral body wall, is bounded by a well 



* Woodward, Monograph of Brit. Fossil Crustacea, p. 122. 



