MANUAL 



OF 



CONCHOLOGY; 



Structural and Systematic. 



WITH n.LUSTRATIONS OF THE SPECIES. 



By GEORGE W. TRYON, Jr. 



CONTINUED BY 



HENRY A. PILSBRY. 



Vol. XIII. 



ACM^ID.^i, LEPETID.E, PATELLID.E, TITISCANIIDtE 



PHILADELPHIA : 



Published by the Conchological Section, 



ACADEMY OF NATURAL SCIENCES, COR. I9TH AND RACE STS. 



