198 



Dimension of 

 valves. 



Compared 

 with other 

 species. 



of these ridges are widely separated (owing to the resorption of the 

 umbo ?) and so appear more transverse there, than farther toward the front 

 of the valve. 



Size. Ventral valve ; length, 12 mm. width, 9 mm. depth, mm. 



Horizon and locality. Slaty seams of the calciferous gray flags of 

 Band C. 2 a. (also in Assise C. 2 b.) at McLean brook, Mira river, Cape 

 Breton, N.S. 



The folowing are dimensions of valves of this form. 



VALVES OK LINGULEPIS STABRI, MOT. EXIGUA FROM BAND C. 2 a. 



The ventral is about two fifths longer than wide, and the length and 

 width of the dorsal valve are about equal. 



The acuminate beak of the ventral is usually broken off, otherwise 

 the disparity in the length of the valves would be greater. 



This form differs from Lingulepis acuminata of the Potsdam sand- 

 stone of the St. Lawrence valley (Beverly, Ont,) in the bluntness of the 

 dorsal valve behind, and in the possession of a median sulcus ; the valves 

 of the Cape Breton form also have a scabrous surface. The ventral is 

 flatter at the umbo and in both valves the muscle scars are in a more 

 advanced position than they are in L. acuminata. 



From L. pinnceformis of the Sb. Croix sandstone it differs in its rougher 

 surface, less acuminate umbo, and in the advanced position of the central 

 muscle scars. 



From L. cuneola Whitfield it differs in its larger size, greater flatness, 

 and more obtuse umbo of the dorsal valve. In form and size it is inter- 

 mediate between L. acuminata and L. cuneola. 



