CONTRIBUTIONS TO PALAEONTOLOGY. Ill 



GENUS BEYRICHIA (M'Coy). 



BEYRICHIA PUNCTULIFERA ( n. s.). 

 Carapace valves minute, semioval, almost equilateral, the anterior 

 end very slightly narrower, convex and abruptly bending down- 

 wards to the dorsal margin ; marginal rim well developed, and 

 sharply elevated on the ventral and lateral margins. The surface, 

 at the more prominent part above the centre, and just at the 

 bending towards the dorsal margin, is marked by two very pro- 

 minent nodes, which are nearly equidistant from the margins and 

 from each other. The entire surface is punctate with minute 

 rounded pits. 



This species is scarcely more than the twentieth of an inch in height ; 

 but it is distinguished by the minutely punctured surface and very promi- 

 nent dorsal nodes. 



Geological formation and locality. In the shales of the Hamilton group: 

 in Ontario county, N.Y. 



GENUS LEPERDITIA ( Rouoult). 



LEPERDITIA CAYUGA ( n. s.). 

 Valves strongly convex, subovate, length about once and a half 

 the width, subtruncate at the anterior end; ventral margin some- 

 what abruptly curved, the greatest width a little posterior to the 

 middle. The left valve is apparently thickened towards the ven- 

 tral margin; but the specimens are in such a condition as to 

 afford no satisfactory evidence of the surface-markings. 



Geological formation and locality. In the Corniferous limestone : at 

 Rlanding's quarry, Springport, near Cayuga lalie, N.Y. 



LEPERDITIA SPINULIFERA (n.s.). 



Minute, ovoid, length less than one-sixteenth of an inch. Valves 

 most convex and a little gibbous towards the posterior end. An- 

 terior tubercle strongly developed, and close to the dorso-lateral 

 angle; the antero- central portion a little depressed, with a very 

 minute and scarcely defined tubercle : the posterior end is ob- 

 liquely subtruncate and very obtuse; the posterior dorso-lateral 

 angle marked by a distinct node, and the posterior ventro-lateral 



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