MANUAL 



OF 



ONCHOLOGY; 



STRUCTURAL AND SYSTEMATIC. 



WITH nj^USTKATIOXS OF THE SPECIES. 



BY GEORGE W.^RYON,) JR. 



CONTINUATION BY ^/ 



HENRY A. PILSBRY, 



CONSERVATOR OF THE CONCHOLOGICAL SECTION OF THE ACADEMY OP 

 SCIENCES OF PHILADELPHIA. 



Vol. XV. 



POLYPLACOPHORA, 



(Chitons.} 



ACANTHOCHITID.E, CRYPTOPLACID^E AND APPENDIX. 

 TECTIBRANCHIATA. 



PHILADELPHIA : 

 3?u.blish.ed by Concliological Section, 



ACADEMY OF NATURAL SCIENCES, 



OF PHILADELPHIA. 



1893. 



