128 HELICID^. 



ground, and keeps itself hidden the greater part of the 

 time. 



The first description of this shell was pubHshed by 

 Mr. Say, In the Journal of the Academy of Natural 

 Sciences of Philadelphia, in January, 1821. Early in 

 1822, it was indicated by F^russac in his^Tableau Syste- 

 matique, as ff. Knoxvillina, as was afterwards shown, 

 when the explanation of the supplementary plates of his 

 work was published, in which the figure of this species 

 is referred to as H. Knoxvillina of his TaUeau, and as 

 M. elevata of Say. Mr. Say's description having been 

 published a year before the name of Ferussac, which 

 was unaccompanied with specific characters to enable 

 the reader to identify it, should give the name first 

 imposed the precedence, and I therefore retain it. 

 M. D'Orbigny, in his Synopsis of the land and fresh 

 water shells of South America, published in Guerin's 

 Magasin de Zoologie for 1835, has applied the same 

 name to one of the species described by him. He was 

 doubtless Ignorant that it had been pre-occupied, and 

 will of course replace it by another, when the fact is 

 known to him. On careful comparison of specimens of 

 Mr. Lea's H. Tennesse'ensis with the inner whorls of this 

 species, there can be little doubt that it is the same shell 

 in an immature state. 



