1915] 



The Ottawa Naturalist. 



41 



Plethopeltis 



saratogensis 



Index ; 75. 



Convexity ; great. 



Eyes ; close to glabella . 



Cephalon ; unvariable, wider than 

 long, never upturned at anterior 

 margin. Posterior development 

 into nucal spine. 



Glabella ; circum -glabellar furrow 

 faint to strong, 2 pairs of faint 

 glabellar furrows and median 

 ridge. 



Plethopeltis 



saratogensis 



Index; 75. 



Convexity ; great. 



Eyes ; close to glabella. 



Cephalon ; unvariable, wider than 



long, never upturned at anterior 



margin. Posterior development 



into nucal spine. 

 Glabella ; circum-glabellar furrow 



faint to strong, no glabellar 



furrow-, no ridge. 



Agraulos 



ceticephalus 



Index ; 63 . 



Convexity ; low. 



Eyes ; farther apart than in preced- 

 ing. 



Cephalon; variable, from wider than 

 long to longer than wide, anterior 

 margin slightly upturned in some 

 specimens. No nucal spine. 



Glabella; no circum-glabellar furrow, 

 4 pairs of glabellar furrows, ridge, 

 eye lines. 



Plethopeltis 



armatus 



Index ; 88 ? 



Convexity ; great. 



Eyes ; close to glabella. 



Cephalon; only one known. No 

 signs of upturning of anterior 

 margin. Nucal spine better de- 

 veloped than in 1 and 2. 



Glabella ; circum-glabellar furrow 

 faint and dying out anteriorly. 

 No glabellar furrows. No ridge. 



Characteristics common to 1, 2 and 4. 



1. Great convexity. 



2. Eyes close to glabella. 



3. Cephalon never upturned at anterior margin. 



4. Facial sutures more nearly similar. 



5. Circum-glabellar furrows similar in outline and roughly paralle 



