J 



viii CONTENTS. 



PAGE 



VI. Of zoological foci, or points of oeigin whence 



GENEKA AND SPECIES AEE DERIVED, . . . 141 



VII. Of the introduction op foreign species into the 



UNITED ^ATES, . 150 



Table of Foreign Species recorded by Authors as 

 ^ observed in the United States, . . . .159 



\ Table of the Distribution of Species inhabiting the 



United States, in other parts of America, . .162 

 ) VIII. Of the distribution of genera and species in the 



UNITED states, COMPARED WITH THAT IN EUROPE 

 AND SOUTH AMERICA, 163 



IX. Geological relations, 176 



X. Habits and faculties, 187 



XI. Special anatomy of the terrestrial gasteropoda 

 of the united states, by JOSEPH leidy, m. d., of 



PHILADELPHIA, 198 



Introduction, 198 



Chap. I. General Remarks upon the exterior form 

 and Structure of the Terrestrial naked Gastero- 

 poda, 199 



Chap. II. General Remarks on the Terrestrial Tes- 

 taceous Gasteropoda,) 201 



Chap. III. On the Tegumentary Covering of the 

 Terrestrial Gasteropoda, . . *' . . . 203 



Chap IV. Of the Digestive Apparatus, . . 206 



Chap. V. Observations on the Tissues of the Diges- 

 tive Apparatus, 216 



Chap. VI. Of the Generative Apparatus, . . 217 



Chap. VII. General Remarks upon the Junction of 

 different portions of the Generative Apparatus, 

 and the Structure of its Tissues, . . . 232 



Chap. VIII. Of the Respiratory and Circulatory 

 Apparatus, 235 



Chap. IX. On the Nervous Centres and the Distri- 

 bution of the Nerves, 239 



Chap. X. On the Organs of Especial Sense, . 243 

 References to the plates, 249 



