CONTENTS 



SIXTH VOLUME 



BY JOHN G. ANTHONY. 



PACK 



Descriptions of new Fluviatile Shells of the Genus Melania Lam., from 



the "Western States of North America 80 



Descriptions of new species of Ancylus and Anculosa, from the Western 



States of America 160 



BY THOMAS BLAND. 



Note on the Geographical distribution of the Terrestrial Mollusks which 



inhabit the Island of St. Thomas, W. 1 74 



On the absorption of parts of the internal structure of their Shells, by the 

 animals of Stoastoma, Lucldella, Trochatella, Helicina, and 



Proserpina 75 



On Proserpina opalina, C. B. Adams, and Helix proserpinula Pfr. . 77 

 Notes on certain Terrestrial Mollusks which inhabit the West Indies . 147 

 Descriptions of two new species of North American Helicid^e . . .277 

 Remarks on certain species of North American Helichle . . . 280,336 



BY J. CARSON BREVOORT. 



Note to the description of Selene argentea of Lacepede, in Vol. V., Annals 



Lye. Nat Hist N. Y. 30 



BY THE HON. E. CHITTY. 



Description of two new species of Cylindrella, from Jamaica, W. I. . 155 



BY JAMES D. DANA. 



On the Homoeomorphism of Mineral Species of the Trimetric System , 37 



BY THE REV. S. C. FAIRBANK. 



Observations on the animal of rotella Lam 35 



BY THEODORE GILL. 



Description of a new species of the Genus Cypraea, L 255 



Synopsis of the Fresh-Water Fishes of the western portion of the Island 



of Trinidad, W. 1 363 



