DIBRANCHIATA I OCTOPODID^E. 



473 



naut sits in its shell, with its siphon turned towards the 

 keel, and its dorsal, sail-shaped arms closely applied to 

 the shell, and swims by ejecting water from the funnel. 



Fig. 375- 



Argonaut, or Paper-Sailor, A rgottauta argo, Linn. One fourth.* Warm Seas. 



This is the Nautilus of Aristotle, who described it as sail- 

 ing on the surface of the sea, with its sail-shaped arms 

 spread to the breeze ; a mere fable. 



OCTOPODID^E. - - This Family comprises cephalopods 

 with eight arms which are similar, elongated, and united 



Fig. 376. 



Octopus tvberculatus, Bl. One fifth. Mediterranean. 



at the base by a web ; and whose shell is represented by 

 two short styles imbedded in the substance of the mantle. 



* One fourth of the linear dimensions. So in all similar cases. 



