EURYPTERUS SHALES OF THE SHAWANGUNK MOUNTAINS 309 



characters. Occasionally a large segment is recognizable, and the 

 figures cited show such parts as are more or less definitely deter- 

 minable. Thus we have the terminal joints of a long cylindrical 

 appendage [pi. 7, fig. i] which evidently represents the long fifth 

 leg in Stylonurus. Figure 12, plate 6 and figure 9, plate 8 are 

 also long, slender leg joints which probably pertain to small indi- 

 viduals of the same genus. Some of the abdominal segments are 

 noteworthy for their lobation, a large one is shown in figure ii, 

 plate 6 and smaller ones of the same type in figures 9 and 10 of 

 the same plate. The largest of these has been so subjected to 

 lateral compression by shearing that the left moiety has been dis- 

 torted beyond recognition, while the same pressure has developed 

 the lobar depression at the right into a distinct break or suture. 

 Such lobed segments are rare in all Eurypterids but are especially 

 noteworthy in a species which has been described by Fr. Schmidt 

 as Stylonurus? simonsoni from the Upper wSiluric of 

 Rotzikiill, Oesel.^ The principal specimen on which this species is 

 based consists of a part of the underside of the head with the oper- 

 cular plates and 6 to 7 abdominal segments. In all these the dorsal 

 furrows are sharply defined and divide the segments into a convex, 

 broad median part and flat lateral portions which can not be regarded 

 as having any relation to the so called "epimera" of Pterygotus. It 

 is true that in typical expressions of Stylonurus such as S. 1 o g a n i 

 Woodward, and S. excelsior Hall there is no evidence of such 

 lobation of the abdomen and though Schmidt has found with these 

 abdominal parts the long leg joints just as we have similar parts 

 associated in the Shawangunk shale there is very excellent reason 

 for the presumption that we are here dealing with creatures which 

 when more fully known will prove to be generically distinct from 

 Stylonurus. The great size attained by some of these bodies in the 

 Shawangunk shale is notable, and in contrast with the rather 

 diminutive series of forms we have been dealing with. Some of 

 the creatures must have attained a length of 3 to 4 feet, but per 

 contra, this would be a small size for Stylonurus, the large forms 

 of which have been shown by Woodward and by Beecher to have 

 reached a length of 7 to 8 feet. 



Phyllocarida 



Plate 6, figure 13; plate 8, figures 12, 13, also 14-21 (?) 



Two very different species of Phyllocarids are indicated by the 

 caudal parts as shown on plate 8, figures 12 and 13, one having 



^Bul. de I'Acad. Imp. des Sciences de St Petersburg. 1903. 5 ser. 20:199. 



