ACHAT1NA. 991 



in the North-western Territory, and was published and 

 figured in the Appendix of the Narrative of the Expedition 

 to the St. Peter's River, in 1824. From that date un- 

 til the year 1844, it remained unseen by naturalists, and 

 was regarded as a species of doubtful authenticity. An 

 anonymous writer in the American Journal of Science 

 supposed that it was the immature spire of a species of 

 Pupa ; an opinion that seemed to be confirmed by refer- 

 ence to Mr. Say's figure. In the last named year, how- 

 ever, it was rediscovered by Dr. Mighels, under damp 

 leaves, in company with Helix arborea, lineata, and stria- 

 tella, in a grove of oaks in Portland, Maine ; a locality 

 a thousand miles distant from the original place of dis- 

 covery. It proves to be a distinct and well characterized 

 species, not liable, when once seen, to be confounded with 

 any other. 



GENUS ACHATINA, LAMARCK. 



GENERIC CHARACTERS. 



ANIMAL. In its external form and characters, it 

 agrees with the animal of Helix and Bulimus. 



SHELL. Form ovoid or turreted, generally thin and 

 delicate in structure, sometimes transparent, oftentimes 

 reversed. The aperture is ovate, more or less elongated ; 

 the lip is simple, and sometimes a little everted, but never 

 reflcxed. The columella is usually plain and rounded, 

 but in some groups it is contorted, or bears a lamella 



