434 



Silurian and Devonian Fossils of Canada. 



acterised by the strong, rounded carina, which extends from the 

 umbones to the posterior ventral angle. 



Locality and Formation. — Occurs at Pointe Claire and in nu- 

 merous localities in the valley of the Ottawa in the top of theChazy, 

 throughout the Birdseye and Black River limestones, and in the 

 base of the Trenton. 



Collectors — Sir W. E. Logan, A. Murray, J. Richardson, E. Bil- 

 lings. 



Ctrtodonta Canadensis (Billings). 



Fig. 8. 



Fig. 9. 



Fig 10. 



Figure 8. A small specimen from the north side of St. Joseph's Island, 

 Lake Huron. 

 " 9. An elongated variety from the lower beds opposite the foot of 

 timber-slide, 4th Chute of the Bonne chere. 

 Fig. 10. A large specimen from Pauquette's Rapids. 



Description. — Transversely broad-oval ; anterior, posterior, and 

 ventral margins, and also the posterior half of the dorsal margin 



