92 Cinciiinaii Society of Natural Histoi y. 



the victims of the inevitable fiat of progress, or have yielded 

 to the changing environments of the ages, their record is the 

 same as that of those in existence. The fore front of modern 

 investigation should march in this line, and those who prefer 

 to belittle the whole manner of the past and present working 

 of this grand harmony of natural law, should be left to play 

 at scientific study with those who prefer such methods. The 

 true naturalist can not afford it. 



NOTES ON THE LAND SHELLS OF RO.\N MOUNTAIN AND 



VICINITY. 



1. Mesodon albolabris, Ssiy. This species occurs here, with 

 the others of this group. It has its typical form, but there 

 occur varieties uniting it with the following. 



2. Mesodon major, Binney. I long considered this form to 

 be a distinct species. The late Thos. Bland, the highest 

 American authority on our land shells, regarded it as a variety 

 of the above. There are forms of a nature to puzzle the 

 naturalist, uniting this and the following. 



3. Mesodox a>idreu'si, W. G. Binney. This form occurs at 

 all elevations, from the plateau to the summit of Roan, and 

 exhibits, as might be inferred, very great varietal differences. 

 Individuals from the foot of the mountain are larger, heavier 

 and more uniform in color, the shells being of a greenish 

 white. Those from the top are thinner, smaller and often 

 very dark smoke color — very beautiful shells. 



4. Mesodon e.xoletus, Binney. This species occurs some- 

 what sparingly, some of the forms being typical and others 

 without the parietal tooth. Having collected and carefully 

 prepared several hundred specimens of the four species above 

 enumerated, I am prepared to say and to show, that while 

 types of each species as described may be selected, it is not 

 difficult to so arrange the whole series, by intergrading varie- 

 ties, as to leave the question of specific distinctness in doubt, 

 so far as the shells are concerned. The comparative anatomist 

 might find slight differences in the animals, but this is what 

 should be expected. There is no collection of individuals of 

 any species that does not carry with it forms stamped with 

 the law of variation, which is as persistent and as self-asserting 



