Hinge teeth taxodout; male and female shells 

 alike; embryo a lasidium. 



I 



f Spatha Lea. 

 Miitela Scopoli. 

 Chelidonopsis Ancey. 

 Brazza'ti Bourguignat. 

 Pleiodon Conrad. 

 Monocondyla'a d'Orbigny. 

 Ilieringclla Pilsbry. 

 Fossula Lea. 

 Glabaris Gray. 

 Leila Gray. 

 Mycetopoda d'Orbigny. 



In the preparation of tbis work I have received uniform courtesy and 

 kindness from students and collectors generally. I am under especial 

 obligations to Mr. Edgar A. Smith, of the British Museum, for exam- 

 ining and reporting on the original manuscript of Solander, and to Mr. 

 H. A. Pilsbry, of the Academy of Natural Sciences of Philadelphia; 

 Mr. A. G. Wetherby, of Magnetic City, North Carolina; Dr. H. von 

 Ihering, Museo Paulista, San Paulo, Brazil; and Mr. H. Suter, Christ 

 Church, New Zealand, for repeated assistance and advice. Mr. L. E. 

 Daniels, of La Porte, Indiana; Mrs. George Andrews, of Knoxville, 

 Tennessee; Hon. J. D. Mitchell, of Victoria, Texas; Mr. Berlin H. 

 Wright, of Penn Yan, New York; Mr. Bryant Walker, of Detroit, 

 Michigan; Dr. W. S. Strode, of Lewistown, Illinois; Mr. H. M. Kelly, of 

 Mount Vernon, Iowa; Mr. William Moss, of Ashton-under-Lyne, Eng- 

 land ; and many others have contributed valuable material for study. 



