58' PALAEONTOLOGY OF KENTUCKY. 



There are from twenty to twenty- four ribs on each valve. Some concentric 

 lines of growth are visible, but whether the shell possessed other surface- 

 markings can not be found out in the silicified condition of the shells, inas- 

 much as the silicification generally obliterates the finer striae. I have placed 

 these shells, of which I possess only the two individuals figured on plate 

 XXIX., as Pent, knighti, though 1 have never seen of that species any correct 

 and detailed description, nor any reliable figure, except those in Ly ell's Ele- 

 ments of Geology and in Woodward's Manual of the Mollusca. I hope my 

 identification to be correct, but if there should be a specific difference, it will 

 soon be found out by geologists, who have access to better libraries and muse- 

 ums than the city of Louisville offers to her scientists. 



Formation and Locality. In the Corniferous rocks near Louisville, in Kentucky and Indiana; of 

 exceedingly rare occurrence. The two specimens in my cabinet, as far as I know, are the only representa- 

 tives of this species in the seven or eight collections of the Falls Cities, as Louisville, Jeffersonville and 

 New Albany are often collectively named. 



Fentamerus littoni. HALL. 



Plate XXVII., figures 12 and 13. 



Pentamerus littoni, Hall. Pal. N. Y M Vol. 3, page 262. 

 Penlamerus littoni, Hall. 24th Kep. N. Y. St. Mus., p. 1861872. 

 Pentamerus littoni, Hall. 27th Kep. N. Y. St. Mus., pi. 10, figs. 8 and 91875. 



Shell ovoid, somewhat elongate. Dorsal valve moderately and regularly 

 convex from base to umbo ; beak strongly incurved under the beak of the 

 opposite valve. Ventral valve very gibbous ; beak sub-attenuate, incurved. 



Surface marked by about eighteen to twenty and more simple, sub -angular 

 plications. There is a broad, concave, smooth space on each side below the 

 beak of the ventral valve, and a much narrower space on each side of the 

 dorsal valve. (Hall.) A large specimen of this species, in my cabinet, meas- 

 ures eleven lines in length, about the same in width, and nine lines in thick- 

 ness. 



My figure is a copy of Prof. Hall's figure in the 27th Eeport. At the time 

 when my plates were made I had no fit specimen to copy, and Dr. Knapp's 

 shell was absent from the city. This species is associated with, and probably 

 related to, Pent, nysius. 



Formation and Locality. It occurs in the Niagara rocks near Louisville, Ky., where it is one of 

 the rarest species. At present my cabinet contains several fair specimens. 



