113 



The dorsal valve is oval in form, and has a somewhat depressed band 

 along the middle, for most of its length, but otherwise it is evenly sloped 

 down to the margin; some examples are elevated along the middle in the 

 interior quarter of the valve, forming a kind of spout at the front. The 

 interior has a median band or callus extending three quarters of the 

 length of the valve, and the lateral septa extend two thirds of its length; 

 the marginal grooves (vascular trunks ?) also show along this portion of 

 the valve, and in front of it are forked. There are several fine ridges 

 close together, along the median band, the two outer of which end at the 

 mid-length of the valve. 



Sculpture. This, as mentioned in the original description, is of fine 

 concentric ridges, of which there are about fifteen in the space of one 

 millimetre ; some examples have as many as twenty to a millimetre on the 

 sides of the valves ; these are crossed by close-set, minute, less conspicu- 

 ous radiating striae, that give a beaded appearance to the edges of the 

 concentric ridges ; there are also a number of growth grooves, marking 

 resting stages in the growth of the valve. 



Size. Length 10 mm.; width 6 mm.; depth of each valve about 1 mm. 



Horizon and locality. In Assises E. 3 c, and e, Upper Etcheminian, 

 at Dugald brook, and f, at Gillis' Indian brook, Escasonie, N.S. 



The following are characters of the valves from the three horizons : 

 VALVES of Leptobolus collicia from E. 3 e. 



Dimensions 

 &c. of valves 

 in assise E 3e. 



8 C. R. 



