Y iii CONTENTS. 
PAGE 
VI. Of zoological foci, or points of origin whence 
GENERA AND SPECIES ARE DERIVED, . . . 141 
VII. Of the introduction of foreign species into the 
UNITED STATES, . 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, . . 1C2 
VIII. Of THE distribution of genera and species IN THE 
UNITED STATES, COMPARED WITH THAT IN EUROPE 
AND SOUTH AMERICA, 1G3 
IX. Geological relations, 17G 
X. Habits and faculties, 187 
XI. Special anatomy of the terrestrial gasteropoda 
OF THE UNITED STATES. BY JOSEPH LEIDY, M. D., OF 
PHILADELPHIA, 19S 
Introduction, 19S 
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 Tegumental-}- 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, 2S5 
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 
