MANUAL 



OP 



ONCHOLOGY; 



STRUCTURAL AND SYSTEMATIC. 



WITH ILLUSTRATIONS OF THE SPECIES. 



BY GEORGE W. TRYON, JR. 



CONTINUED BY 



HENRY A. PILSBRY. 



Vol. XIII. 



ACMJEIVAL, LEPETID^, PATELLIDyE, TITISCANIID^E. 



PHILADELPHIA : 

 Published by the Conchologieal Section, 



ACADEMY OF NATURAL SCIENCES, COR. igTH AND RACE STS. 

 1891. 



LIBRARY 



UNIVERSITY OF CALIFORNIA 

 DAVIS 



