14 PALJSONTOLOGY OF NEW-YORK. 



LIXGULiE OF THE CHEMUNG GROUP. 



Linsrula nielie ( n. s.). 



PLATE I. 



Shell elliptical ; length and breadth about as three to two, the width 

 often a little greater ; moderately convex, the umbo prominent, and 

 below it begins a narrow flattened space, which, very gradually wide- 

 ning, reaches to the base. (This feature is noticed on the ventral valves.) 

 Sides curving, the margins flattened or a little recurved. Beak of the 

 ventral valve extended and acute ; and in partially exfoliated speci- 

 mens there is a depressed sublinear area reaching more than one-third 

 the length of the shell, and margined on each side by a sharp line. 



The specimens, which appear to be the ventral valves of the same species, 

 are obtuse at the cardinal extremity, and proportionally wider towards 

 the base. The most extreme example of this kind is shown in fig. 3, 

 while fig. 4 is the extreme of the other form. The surface characters 

 are the same in all the specimens, and, on the exterior shell, consist of 

 fine concentric striae which are crowded at intervals into ridges, giving 

 an undulating surface. On the exfoliated fossil, the concentric wrinkles 

 are preserved with faint impressions of the striae ; and obscure radia- 

 ting coarser striae mark the surface, becoming stronger towards the 

 margins, and terminating just within the edge in minute depressions 

 or puncta. 



This species, in some of its forms, resembles the L. spatulata, but is larger, and 

 also very distinct in the details of its surface markings. 



This species occurs at Chagrin Falls, Ohio, in strata of the age of the Chemung 

 group. 



