22 Observatio7is on the Terrestrial 



This is one of the first species described by Say. He was 

 l^robably unacquainted at that time with the Vallonia pulchella 

 of Europe, as he makes no remarks on the resemblance of his 

 species with the European form. Stimpson, Kirtland and Dekay 

 retain the specific name of mimita for this shell, while Binney, 

 Gould, W. G. Binney, Adams, Mighels, and all the European 

 writers unite it with V. pulchella. Dr. Binney expressed his 

 opinion that this species was not identical with V. pulchella, as 

 he could not perceive hoAv an introduced species could have 

 penetrated regions so remote from the coast. (Binney's Mon., 

 Vol. II. p. 176.) W. G. Binney has in his possession notes of Mr. 

 Say never published, in which he (Say) acknowledged an identity 

 between the two species. When we consider how widely and 

 abundantly this species is distributed throughout North America, 

 no less abundant in the far west than on the Atlantic coast, we 

 certainly have reason for believing this species indigenous. 

 The occurrence of the supposed variety, V. costata in this country 

 has been cited as an evidence of the identity of V. minuta with 

 V. pulchella. I cannot see that the occurrence of this ribbed 

 variety in the United States proves any identity between the two 

 species, for it seems probable that two species so intimately re- 

 sembling each other would be liable to exhibit similar modifica- 

 tions ; examples are common wherein closely related forms present 

 similar phenomena of variation ; among the Helicidae for instance, 

 we have the difference in the coloring both of the animal and 

 shell, the presence or absence, or the variability in the arrange- 

 ment of teeth within the aperture of the shell, the closed or open 

 umbilicus ; or, among the Unionidae we have in close resembling 

 species an identical mode of variation, either in the inflation or 

 contraction of the shell, in the elongation or truncation of the 

 anterior region, or, in the presence or absence of radiating lines 

 of coloring. Vallonia costata however, I believe to be a distinct 

 species. 



In the following comparisons numerous specimens from various 

 localities in Europe, and from Ohio, New York, Massachusetts, 

 and Maine, have been examined and the differences pointed out 

 have been verified in every specimen examined. 



