CANADIAN FOSSILS. 9T 



IV. Leperditia amtgdalina, Jones. 

 Plate XI. Figs. 18, 19. 



(Annals of Natural History^ 3d series, vol. i. page 341.) 



Several specimens of a dark-grey limestone, from near L'Orignal, 

 are rich in separate valves of a handsome Leperditia^ which at 

 first sight has much the aspect of Isochilina Ottawa; but it is 

 larger, blacker, and has a proportionally shorter hinge-line, the 

 hinder portion of the valves being boldly and obliquely rounded, 

 forming about one-third the length of the carapace ; though the 

 valves have a marginal rim, this is only on the two ends, being 

 wanting below, where the middle third of the ventral border is 

 turned in, overlapping on the right, and overlapped on the left side. 

 The surface is smooth ; the eye-spot prominent, and accompanied by 

 a slight, irregular nuchal furrow ; muscle-spot indistinct. The cara- 

 pace is JL inch long, /^ in. broad, and ^V in. thick, and most convex 

 at the anterior third. 



Though numerous in the rock, the individuals are not massed 

 together in layers, as are the Isochilince at L'Orignal, Grenville, and 

 White Horse Rapids. 



Locality and Formation. — One mile west of L'Orignal, Chazy, 



Collector. — R. Bell. 



Genus Isochilina*. Subgenus of Leperditia. 



Equivalve; the margins of the valves meeting uniformly, not over- 

 lapping as in Leperditia; greatest convexity of the valves either 

 central or towards the anterior portion. Eye-tubercle present. 

 Muscular spot not distinct externally. 



V. Leperditia (Isochilina) Ottawa, Jones. 

 Plate XI. Fig. 14. 



{Annals of Natural History^ 2d series, voL i. p. 248, plate x. fig. 1.) 



Length I, breadth J^ inch. 



Leperditia-like in outline, somewhat elongate, smooth; marginal 

 border distinct, frequently seen to be marked by a line of small, 

 distinct pits ; eye-spot distinctly raised. 



* Equal lip. 

 G 



