CRUSTACEA— OSTRACODA. 



339 



3. B. tinea Matthew. (Fig. 1652,^-^.) Cambric. 



Height greater than length of hinge Hne ; dorsal depression large. 

 Middle Cambric, Protolenus beds of New Brunswick. 



4. B. planata Matthew. (Fig. 1652, /l) 



Cambric. 



Fig. 1652. a, b, Hipponicharion cavatum ; 

 c, d, H. minus ; e-g, Beyrichona tinea ; h, B. 

 planata. (All after Matthew, enlarged.) 



Fig. 1653. Leperditia fabu- 

 lites ; left valve. ( After Ulrich. ) 



Hinge line longer than height of valve ; dorsal depression smaller 

 than in preceding. 



Occurs with preceding. 



ni. Leperditella Ulrich. 



Similar to Leperditia but the left instead of the right valve is 

 the larger and has a groove within its ventral border into which 

 the simple edge of the right valve is received. Eye tubercle want- 

 ing while a more or less obscure broad depression is generally 

 present in the central part of the dorsal half. Length i to 3 mm. 

 Genotype Leperditia inflata Ulrich. About fifteen species. Or- 

 dovicic. 



5. L. inflata Ulrich. (Fig. 1656, a-c.) Ordovicic. 



Valves strongly convex, giving the shell an inflated appearance. 

 Lowville and Black River formations of Kentucky, etc. 



IV. Leperditia Rouault. 



Shell suboblong with an oblique backward swing, comparatively 

 large, 2 or 3 mm. to 22 mm. in length; dorsal edge straight, gen- 

 erally angular at the extremities ; ventral outline rounded, greatest 

 thickness in the ventral half, the lower edge being usually also 



