TRILOBITA—OPISTHOPARIA. 281 



Length of cephalon 25 mm. ; width minus the free cheeks at the 

 anterior end 25 mm. ; at the posterior end 40 mm. 

 Upper Cambric (Bretonian) of Cape Breton. 



XXVIII. Peltura Milne-Edwards. 



Cephalon semicircular. Glabella wide and long, extending nearly 

 to the frontal margin. Eyes small and far forward. Genal mar- 

 gins of cheeks rounded. Axis wider than the pleura. Pygidium 

 shield-shaped, well developed, with notched margin. Upper 

 Cambric. 

 65. P. scarabeoides (Wahlenberg). (Fig. i58i,a, &.) Cambric. 



Glabella very large. (Type of genus.) 



Upper Cambric (Bretonian) of Cape Breton; also Europe. 



XXIX. Ctenopyge Linnarsson. 

 Cephalon like Sphceropthalmus, but the middle lobe of the body 

 narrower proportionally; the posterior portion of the fixed cheeks 

 broader. Glabella reaches anterior margin ; facial suture a regular 

 sigmoid curve. Pygidium large, its divisions ending in long spines. 

 Cambric. 



Fig, 1582. a\ y, Sphceropthalmus alatus, var. canadensis^ narrow form,X 4; ^^t^y 

 Ctenopyge acadica^ cephalon and free cheek, X 3 5 '^j section of thorax, X 35 'A <?> 

 hypostoma, X 4- (After Matthew.' 



