NOTES ON GASTEROPTERON MECKELII. 259 



«yes are visible externally, the animal probably can 

 ^ee to some extent, for visual organs exist, although 

 beneath the outer skin. The branchial plume is 

 exposed on the right side of the back, and the 

 posterior extremity of the mantle terminates in a 

 short bright-red tentacular process, the precise 

 function of which is not at present understood. 



G^steropteron is provided with a minute internal 

 shell. It IS only about one-fiftieth of an inch in 



fnT' nl^' r^^^^^y^^y ^^^-' «b^Ped like a Nautilus, 

 and protects a minute spiral lobe of the liver 



Thxs animal was originally described by Kosse in 

 ims. It was subsequently investigated by DeUe 

 Chiaje. Cantraine, Souleyet, and Krohn, and finally 



thll^TZo^^"''''''^ ^y Vayssiere appeared in 

 the Annales des Sciences naturelles, vol. ix. (1879-80). 



