37^ 



NORTH AMERICAN INDEX FOSSILS. 



13. E. pustulosa Whitfield. (Fig. 1680, f:.) Devonic. 

 Hinge area shorter than in preceding; posterior end more 



sharply rounded, anterior end slightly produced; surface with 

 coarse ridges and pustulose nodes. 

 Chagrin (Erie) shales of Ohio. 



14. E. multinodosa Whitfield. (Fig. 1680, J.) Devonic. 

 Posterior end pointed and pustulose; anterior rounded; hinge 



line short ; valves with short folds near hinge and sharp, irregular 

 quadrate nodes in cephalic region. 

 Chagrin (Erie) shales of Ohio. 



VI. Pephricaris Clarke. 

 Differs from the preceding in the absence of the S-shaped keel, 

 and in a margin with long, curving spines; abdomen with only 



Fig. i68i. Pephricaris horripilata, FiG, 1682. Aristozoe troyensis, left 

 complete, with the carapace spread. (Af- valve enlarged, and right valve. (After 

 ter Clarke. ) Walcott. ) 



three or four segments protruding below the carapace, the last 



two with a long spine on each side. Devonic. 



15. P. horripilata Clarke. (Fig. 1681.) Devonic. 



Spines increasing in length posteriorly, but last four decreasing 

 again ; one carapace with a single oblique fold tapering posteriorly ; 

 telson short, cercopods several times as long, slightly curved. 



Chemung of New York. 



VII. Aristozoe Barrande. 

 Carapace with node on cephalon well developed, but without 

 lateral keels ; but one abdominal segment known, and this is very 



