171 



Another example of the valve with the surface somewhat corroded shows 

 small pits and also anastomosing ridges on the surfrce. 



Size. Length, 4J mm. ; width, 3 mm. ; depth of a valve, 1 mm. 

 Another example is 3^ mm. wide. 



Horizon and locality. Assise, E. 1 e. Lower Etcheminian at Dugald 

 brook, Escasonie, N.S. Scarce. 



A form similar to this in size, though proportionately wider, occurs in 

 the same assise ; and another smaller, broader and flatter, is found in the 

 assize E. 3 e Upper Etcheminian, at the same brook. 



The following are dimensions of some valves : 



E. 1 e. left valve, length 4 mm. width, 3 mm., depth, 1 mm. Dimensions. 



E. 1 e. carapace, " 4 mm. " 3 mm., " 3 mm. 

 E. 3 e. lef o valve, " 4 mm. " 3 mm., " 1 mm. 



Xestoleberis, Sars ('65), as represented by Prof. T. Rupert Jones' species 

 S. Wrightii, from the Ordovician of Kildare, Ireland, is like this in form, 

 but is more tumid, and is not shown to possess an ocular tubercle. 



Mutation PRIMA. PI. XIII, 9 a to c. 



Can. Rec. Sci., Montreal, 1902, p. 462. 



A form resembling this species, but longer and larger, is found in the Mutation 

 gray shale of the volcanic rocks. The example is a complete carapace, p 

 and the valves are crushed somewhat and displaced. There appears to 

 be an ocular tubercle near the anterior end, and the fullest part of the 

 valves is in the lower half. 



Sculpture. The surface is corroded, but there are traces of a fine punc- 

 tatioii and of longitudinal strife on the middle part of the valve. 



Size. Length of a carapace, 5 mm. ; width, 3 mm. ; depth 2J-. 



Horizon and locality. In fine gray shale in the midst of the volcanic 

 rocks of the Coldbrook group of Dugald brook, Escasonie, N.S. Scarce- 



INDIANA LIPPA, PI. XIII., figs. 10 a to d. 



Can. Rec. Sci., Montreal, 1902. p. 463. 



Hinge line more than half of the length of the valve. Caidinal curves Indiana lippa. 

 of moderate length ; anterior marginal curve twice as long as the poste- 

 rior, convexly arched. A very faint elevation in the position of the ocu- 

 lar tubercle : and a very shallow depression behind it. There is a thick- 

 ened and slightly elevated band all around the margin, except at the hinge. 



