8 PALJBONTOLOGY OF NEW-YORK. 



Tho shell u of more equal width throughout and more symmetrically oval, and 

 also much larger than tho L. spatulata of tho Genesee slate. It is likewise more 

 prominent along tho centre of tho upper half of the shell. One valve (the ventral ?) 

 appears to have been more convex than tho other. 



Geological formations and locality. In the shales of the upper part of the 

 Hamilton group, on the banks of Seneca lake. 



Liiigula ligea, var. 



PLATE II. 



The specimens from the lower part of the Portage group are larger 

 than those from the Hamilton group, and have the sides somewhat 

 straighter; while the cardinal extremity is not so rounded, and slopes 

 in nearly a right line on each side of the beak. The surfaces are not so 

 well preserved as in those of -the Hamilton group. This may ultimately 

 prove to be a distinct species. 



Geological formation and locality. In tho arenaceous shales of the Portage 

 group : at the falls below Trumausburgh, New- York. 



Liiigula imhcforiiiis. 



PLATE I 



Lingula palte/ormU : IIall, Thirteenth Report of the Regents on the State Cabinet, p. 76. 



Shell broadly subovate ; sides sloping in a nearly straight line from the 

 beak to half the length of the shell, convex at the umbo and depressed 

 below, the length a little greater than the greatest width, rapidly 

 expanding for about two-thirds the length of the shell, below which 

 it is abruptly rounded : shell thick. Surface marked by strong concen- 

 tric lamellose striae, and, in the exfoliated surface, by fine radiating 

 strisa. 



This species, in general form, resembles the L. spatiosa of the Lower Hclder- 

 berg group, but differs conspicuously in the surface strife ; and among a conside- 

 rable number of specimens, the dimensions are the same as the specimens figured, 

 being nearly two-thirds the length of the Lower Helderl)crg species. 



Geological fomuUion and locality. In the shales of the Hamilton group ; asso- 

 ciated with numerous known fossils in a loose fragment of rock, found in the 

 valley south of Cayuga lake. 



