Silurian and Devonian Fossils of Canada. 437 



Locality and Formation. — City of Ottawa, Belleville, and at 

 Trenton on the bay of Quinte, in the Trenton limestone ; at the 

 Fourth Chute of the Bonne-chere, and also at Pauqnette's Rapids 

 very perfect specimens are common, associated with fossils of the 

 Trenton and Black River formations. 



Collectors.— Six W. E. Logan, J. Richardson, and E. Billings. 



Cyrtodonta sub-truncata (Hall sp.) 



Edmondia sub-truncata, Hall, Palaeontology of New York, Vol. i., page 

 156, Plate 35, Figure 3 c, (not Fig. 9, Plate 34.) 



This species is common in the Trenton and Black River lime- 

 stones of Canada at all the localities above mentioned. The silici- 

 fied specimens shew the internal characters of Cyrtodonta very 

 clearly 



Cyrtodonta sub-angulata (Hall sp.) 



Edmondia sub-angulata, Hall, Palaeontology of New York, Vol. L, page 

 156, Plate 35, Figures 2 a, b. 



A specimen of this species from Pauqnette's Rapids exhibits in 

 the right valve two posterior lateral teeth and an area between 

 the beaks. That portion of the hinge line occupied by the anterior 

 hinge teeth is destroyed, so that their character cannot be observed. 

 There is an ante:ior muscular impression as in the other species. 



It occurs at Banquette's Rapids and at La Petite Chaudiere. 



Cyrtodonta cordiformis (Billings). 



Description. — Sub-rhomboidal ; cordiform ; extremely ventri- 

 cose ; umbones strongly incurved ; obtusely carinate on their up- 

 per side ; the carination extending backwards and diagonally 

 downwards, becoming more rounded and nearly obsolete before 

 reaching the posterior ventral angle ; the hinge.-line is straight, short, 

 and about at right angles to the direction of the carina ; from the 

 extremity of the hinge-line the posterior side slopes abruptly, but 

 with a moderate curve, to the posterior ventral angle ; ventral mar- 

 gin a little convex, and about as long as the posterior side ; ante- 

 rior margin half the length of the ventral, not much curved ; an- 

 terior muscular scar oval and distinctly marked ; surface concen- 

 trically striated. Length of largest specimen examined from the 

 beaks to the posterior ventral angle, thirteen lines ; length of hinge- 



