CONTRIBUTIONS TO PALEONTOLOGY. 2% 



obtusely rounded and produced below, and more acutely con- 

 verging towards the beaks. 

 Surface very gently convex below and a little more convex on 

 the umbo, marked by fine threadlike strise which are sometimes 

 crowded in fascicles. No radiating strias are preserved in the 

 specimen. 



The specimen described is apparently a ventral valve, and preserves some 

 remains of the muscular impression. In form it resembles the L. ligea, but 

 is less convex, and the lower part of the shell is more produced, so that 

 the striae make a more extended curve than on that species, and they are 

 likewise coarser. 



The typical forms of L. ligea are about half an inch in length and one 

 quarter of an inch in width ; and the L. maida has a length of more than 

 three-fourths of an inch, with a width of nearly half an inch. 



Geological formation and locality. In the Moscow shales of the Hamil- 

 ton group : at Moscow, Livingston county. 



'' LINGULA PUNCTATA (n.s.)." 



Shell subelliptical, length and breadth as three to two ; sides 

 parallel ; base subtruncate ; cardinal slopes abrupt, and but 

 little curved ; umbones prominent, somewhat flattened in the 

 middle below the longitudinal centre, the flattened space ex- 

 panding 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 striae. Muscular impressions, in the cast or partially ex- 

 foliated shell, subcordate belov^^, 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 an inch, and the width of the larger 

 specimens is half an inch. The surface marking is peculiar and characteri- 

 stic, the apparent punctate structure being caused by two sets of concentric 

 or irregularly wrinkled stria3, leaving minute pits between them. In this 

 character, which is preserved more or less even upon the casts or exfoliated 

 surfaces, the speeies is rjeadily identified. 



It resembles in general form the L. rcctilatcris 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 : 

 Monteith's point, on Canandaigua lake. 



