PLATE IT. 



!. — View of the dorsal side of a Nautilus removed from its slid], 



CR, crescentic ridge on the posterior tact- of the 1 1. 



HA, dorsal aponeurotic band. 



DM, dorsal portion of mantle. The index line points to a depression in the dorsal side of the body into 

 which (its the involution of the shell. 



DT 2 , second digital tentacle. 



E, eye. 



1 IoA, auricle of hood. 



lloC, Hot', cirri of tentacles composing the hood. 



()'. preocular tentacle. 



Si, base of siphuncle. 



\, backwardly projecting point of dorsal aponeurotic band, which is evidently the cause of the small back- 

 ward projections near the dorsal edges of the septa, shown in Fig. 1. 



y, constriction of the siphuncle where it passes through a septum. 

 200 



