MOLLUSC A. 137 



stalks. In the specimens of the Ocythoe Cranchii, pro- 

 cured during the expedition to the Congo, Dr. Leach ob- 

 served " four oblong spots on the inside of the tube, re- 

 sembling the surfaces for the secretion of mucus, two in- 

 ferior and lateral, and two superior, larger, and meeting an- 

 teriorly. On the rim of the sac, immediately above the 

 branchiae, on each side, is a small, short, fleshy tubercle, 

 which fits into an excavation on the opposite side of the 

 sac." (Phil. Trans. 1817.) 



This animal was long considered as the fabricator of the 

 shell termed Argonauta or Paper Nautilus. The observa- 

 tions of Mr. Cranch, the zoologist to the Congo expedition, 

 were supposed to have demonstrated that the shell is merely 

 the temporary residence of this animal, which it quits at 

 pleasure. The body of the animal does not conform in 

 shape to the cavity of the shell, nor to all its irregularities 

 of surface ; neither is there any muscular attachment be- 

 tween them. " On the thirteenth of June," (says Dr. Leach, 

 when publishing the notes of Mr. Cranch,) " he placed two 

 living specimens in a vessel of sea-water ; the animals very 

 soon protruded their arms, and swam on and below the sur- 

 face, having all the actions . of the common Polypus (oc- 

 topus) of our seas ; by means of their suckers, they adhered 

 firmly to any substance with which they came in contact, 

 .and when sticking to the sides of the basin, the shell might 

 easily be withdrawn from the animal. They had the power 

 of completely withdrawing within the shell, and of leaving 

 it entirely. One individual quitted its shell and lived seve- 

 ral hours swimming about, and showed no inclination to re- 

 turn into it ; and others left the shells as he was taking them 

 up in the net. They changed colour, like other animals of 

 the class Cephalopoda ; when at rest, the colour was pale 



