PLATE I. 



Vui. 1. — A Nautilius seen from the right side, tlie right, half of tlie shell having Ijeen cut away. 

 AV, anterior ventral aponeurotie ImiikI. 

 C, (cirrus of a digital tentacle. 



Csh, cephalic sheath, composed of (he fused slieaths of digital tentacles. 

 CR, crua of funnel. 

 DM, dor.sal portion of mantle. 



E, eye. 



F, funnel. 

 Ho, hood. 



1, involution of shell. 



<)', preocular tentacle. 



O", postocular tentacle. 



PV, posterior ventral ai)oneiirolii- hand. 



S, living chaniher of .shell. 



Si, siphon of shell. 



SI, siphuncle of liody. 



SM, area of attachment of shell muscle. 



Sp, last-formed si>ptum. 



VM, ventral portion of mantle. This is free imm tlie body I'lom tlie edge as far hack as the anterior ventral 



aponeurotic hand. 



I'JS 



