Cambrian Rocks in Cape Breton. 457 



Only one example known, which is supposed to be a 

 right valve. 



Suboval with a long hinge-line, about three quarters of 

 the length of the valve. Anterior cardinal curve short, 

 posterior longer. Anterior marginal curve long, rounded; 

 posterior shorter, rounded forward. The valve is more 

 tumid in the cardinal third, and rounded to the hinge, 

 where there is a low narrow ridge. A thread-like mar- 

 ginal fold is visible in some parts of the margin. 



In this species there is no definite ocular tubercle, but 

 a group of several small tubercles on a slight elevation, 

 occupy its place. The ocular furrow is shallow, and close 

 to the front of the hinge, and extends downward opposite 

 the anterior cardinal curve. 



Sculpture. The surface is covered with distinct pits, the 

 spaces between which become inosculating ridges, subpar- 

 allel to the length of the valve, but tending downward in 

 the direction of the front of the valve ; towards the hiuge 

 line the pitting is very minute. 



Size Length 2\ mm., width 1| mm., depth of a valve 

 nearly | mm. 



Horizon and locality. Assise E. 1. c. Lower Etcheminian 

 Fauna, at Dugald Brook. 



The sculpture, something like that of an Entomis or a 

 Kerbya but finer, separates this little species from the 

 others. 



ESCASONA, n gen. 



A few forms which cannot be referred to any genus of 

 the Eopaltezoic are present at two horizons in the Etch- 

 eminian. The typical form is in one of the highest beds 

 of the Upper Etcheminian. It is short and high and 

 the slight eminence which appears to indicate the ocular 

 tubercle is close to the hinge. There is a long slope from 

 the hinge toward the middle of the valve, it thus resembles 

 Beyrichona ; but it does not have the two strong furrows 



