Fossils of the Chazy Limestone. 



44 



thence sloping abruptly to the hinge line and posterior an<$ 

 ventral margins. 



Length from posterior ventral angle to anterior extremity six 

 lines ; height from ventral margin to posterior extremity of hinge 

 line four lines ; from beaks to- ventral margin three lines ; beaks 

 within one line of most projecting point of anterior extremity; 

 surface apparently concentrically striated. 



Locality and Formation. — Chazy saudstone, three miles east 

 of the city of Ottawa, half a mile back from the river. 



Collector. — E. Billings. 



Vanuxemia Montrealensis. (N. s.) 



Figs. 25, 26. 



Figs. 25, 26.— -Vanuxemia Montr ealensis. 



Description. — Obliquely sub-oval or sub-rhomboid al, with ar? 

 indication of a posterior wing ; surface with fine concentric striae ; 

 length about an inch and a-half. 



The beaks are small, pointed closely, incurved and directed 

 forwards; the umbo is rather strongly elevated and narrowly 

 rounded ; from the umbo the convexity of the valve gradually 

 increases in width, is most prominent about the centre or a little 

 nearer the beak than the centre and from that point diminishes 

 in all directions towards the posterior and ventral margins. The 

 anterior margin near the beak has not been observed ; but, judg- 

 ing from the cast, it does not appear to be alated. From the 

 beak it inclines backward at an angle of about 75° with the hinge 

 line for three-fourths the whole length when it gradually curves 

 to produce the broadly rounded postero-ventral extremity. The 

 hinge line is straight, and its length appears to he about equal to 

 three-fourths of the diagonal of the shell from the beak to the 

 lower posterior angle. The posterior extremity of the hinge line 

 has not been observed ; but it probably forms an obtuse angle 



