lO PALAEONTOLOGY OF NEW-YORK. 



Liiijriila punctata ( n. s.)- 



PLATE L 



SiiELL subclliptical, length and breadth as three to two ; sides pax-allel ; 

 base subtruncate ; cardinal slopes abrupt, and but little curved ; um- 

 bones prominent, somewhat flattened in the middle below the longitu- 

 dinal centre, the flattened space expanding towards the base. Ventral 

 valve a little more convex than the opposite. 



Surface marked by concentric wrinkles ; the entire structure punctate 

 or subpunctate, sometimes corrugate, with extremely fine stria?. Mus- 

 cular impressions, in the cast or partially exfoliated shell, subcordate 

 below, with numerous diverging foliate imprints above. 



The length of the shell varies in different individuals from one-half to three- 

 fourths or even seven-eighths of au inch, and the width of the larger specimens is 

 half an inch. The surface marking is peculiar and characteristic, the apparent 

 punctate structure being caused by two sets of concentric or irregularly wrinkled 

 striae, leaving minute pits between them. In this character, which is preserved more 

 or less even upon the casts or exfoliated surfaces, the species is readily identified. 



It resembles in general form the L. rectilateris of the Lower Helderberg group, 

 but is less rounded on the cardinal slopes and less convex on the lower half of the 

 shell, while the base is much more abruptly truncate. 



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

 telth's Point, on Canandaigua lake; and near Summit in Schoharie county, N.Y. 



Liiigula iiuda ( n. s.). 



PLATE IL 

 Shell subelliptical ; length nearly twice as great as the width ; sides 

 Bubparallel, very slightly curving, the greatest width near the centre ; 

 base truncated ; cardinal slopes rounded, the ventral valve a little 

 more pointed and more convex than the dorsal valve. Dorsal valve 

 nearly flat. Ventral valve, in exfoliated specimens, marked by a de- 

 pressed line down the centre, with indications of foliate muscular 

 impressions upon each side. Surface marked by fine concentric striae, 

 which, on the margins, are crowded and wrinkled. 



