CANADIAN FOSSILS. 39 



C. ASTART.EFORMIS, N. Sp. 



Plate VIII. Figure 7. 



C. crassa, vix semipollicaris, trigona, note curvo, exctlso: mar gin e postico 

 lente concavo, reliquis convexis ; super/icie lineis crebrissimis rugisque 

 concentricis ornatd : dentibus pluribus, fractis. 



A small, thick shell, higher than wide, triangular, with a greatly 

 elevated and somewhat curved beak, and the surface covered with 

 fine equal concentric striee, besides four or five rugae or varices of 

 growth. The posterior side (at least we must suppose this to be the 

 posterior side from analogy with other species of Nucula, — the beak 

 is however extravagantly raised ;) is gently concave without a dis- 

 tinct lunette, the posterior and ventral margins arched ; the whole 

 figure is triangular. 



The interior shews a flat hinge-plate, broadest beneath the beak> 

 but with no cavity for a ligament, which must therefore have been 

 external, though no fulcra are visible. The teeth are numerous and 

 V-shaped, extending far down the posterior hinge-plate, and half-way 

 down the anterior side. They are either absent or very small imme- 

 diately under the beak. 



This beautiful species exactly resembles at first sight one common 

 in the Lower Silurian rocks of Wales, the C. (Nuc.) varicosa, Salter, 

 and it is difficult to say how they differ. But while the Canadian 

 fossil is a solid shell, the British species is a very thin one, and it is 

 the interior cast of the one that resembles the outside of the other. 



Locality. — Allumette Islands. 



Orthis tricenaria, Conrad. 



Decade I. Plate 9. 



Genus Orthis, Dalman. Mollusca Brachiopoda. Family Orthidae. 

 Shell punctate, squarish, rounded, or transversely oblong (the 

 hinge-line generally narrower than the shell), radiately striated 

 or plaited, convex in one or both valves; hinge-line with a 

 fissure open in both valves* ; dorsal valve with divergent short 

 teeth, and a simple cardinal process between them ; muscular 

 impressions roundish, and circumscribed in the dorsal valve. 



* In Orthisina and Streptorhynchus the fissures are closed. These are regarded as 

 subgenera of Orthis by some authors. 



