212 PALEONTOLOGY OF KENTUCKY. 



flange attached to the margin of the shell. It is considered by some geologists 

 as identical with Par. lirata. 



Formation and Locality. In the Corniferous limestone of the Devonian formation in Jefferson 

 county, Ky., and in Clark county, Ind., where it is found rather abundantly, and in well preserved speci- 

 mens, which are always entirely silicified. 



Paracyclas octerlonii. .SP. 



Plate XXXI., figure 18. 



The shell of this species agrees, in every particular, with that of the preced- 

 ing species, except in size and form. It is considerably smaller than elliptica, 

 measuring somewhat less in width, and considerably less in length. Its form 

 is peculiar, having its anterior and posterior margins almost straight and par- 

 allel. Orlando Hobbs, Esq., of Jeffersonville, Ind., presented me with the 

 first specimen of this species, and drew my attention to its peculiar shape, 

 which could not be the result of distortion, inasmuch as the shell did not show 

 the least sign of any violence. Afterwards I came in possession of a great 

 number of specimens, all of which have exactly the same figure ; but I never 

 obtained forms which, as intermediates, could have connected them with the 

 elliptica. These differences are so well marked, and appear to be constant, 

 and I, therefore, considered them sufficient to base upon them a new species. 

 Should hereafter such forms be found, which will connect them with the ellip- 

 tica, they will, even then, retain at least the character of a variety. 



Most all distorted specimens of Par. elliptica, which came under my observa- 

 tion, I found to be compressed in the direction from base to hinge-line ; never 

 in the direction from the front to the rear, which is easily explained by the 

 fact that the Lamellibranchiata generally rest upon the base of their shell, 

 placing the hinge on top. Any compression will be caused by the weight of 

 superimposed bodies, and will result in reducing of the width and enlarging 

 of the length. 



Formation and Locality. This species is found associated with the preceding species in the Cor- 

 niferous limestone of Kentucky and Indiana, at and near the Falls of the Ohio. It is somewhat rare, at 

 least well preserved specimens are seldom found. I have named this species in honor of Dr. John A. 

 Octerlony, of Louisville, Ky., who is not only an excellent physician, but also an ardent student of Natural 

 Sciences, and especially of Geology and Palaeontology 



