160 



Mutation 

 sequata. 



Bradorona 

 obseryator 

 described. 



Mutation ^QUATA. PL XII., figs. 14 a and b. 



Can. Rec. Sci., Montreal, 1902, Vol. VIII., p. 448. 



Anterior and posterior sides nearly equal. The form is oval, and is 

 wide below the cardinal curves, which are long. Anterior as well as 

 posterior marginal curve regularly arched. 



Sculpture. The surface has been corroded, but shows traces of a minute 

 pitting. 



Size. Length and breadth each 3f mm. ; depth of a valve 1 mm. 



Horizon and locality. In Assise E. 3 d. Upper Etcheminian Fauna, 

 at Dugald brook. Rare. 



BRADORONA OBSERVATOR. PI. XII., figs. 15 a to c. 



Can. Rec. Sci., Montreal, 1902, Vol. VIII., p. 448. 



A small species of the same general form as the preceding, but the 

 anterior marginal curve is more oblique on the hinge line, the ventral 

 angle being opposite to the posterior half of the cardinal line ; this 

 (2 mm. long) is considerably more than half the length of the valve. 



The anterior cardinal curve is angulated at each end ; the posterior is 

 a third longer than the anterior. The anterior marginal curve is 

 straightened and is considerably longer than the posterior, which is 

 strongly arched outward. A narrow thread-like marginal fold is visible 

 in some places. A thickened band within the margin, in some places, 

 shows slight protuberences. 



Sculpture. In most examples the surface is scabrous from corrosion, 

 but some show traces of a minute pitting, and near the margins of the 

 valve these pits form continuous rows, or furrows. The mould of the in- 

 terior showing smooth surface having minute punctures. The muscle scar 

 behind the ocular tubercle, is distinct on the mould of the interior of the 

 valve. 



Size. Length 3 mm ; width 3 mm ; depth of a valve 1 mm. 



Horizon and locality. In Assise E. I. d., Lower Etcheminian, at 

 Boundary brook. Common. 



The following are measurements of several valves from this locality : 



Left valve, length 



o ci d 



Carapace 



mm., width 2 mm., depth 1 mm. 

 31 " 3 " "1 " 

 31 d 2& ' (< 3- 

 31 23- " " & " 

 3f " " 2f " " 2 " 



