THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



No. 78. NOVEMBER 1843. 



XXXVII. — On the Structure and Homology of the Cephalic Ten- 

 tacles in the Pearly Nautilus. By Prof. Owen, F.K.S. 



To the Editors of the Annals of Natural History. 



Gentlemen, 

 I HAVE been favoured with a letter from Prof. Vrolik, in which 

 he writes : " We found the situation of the soft parts of the Pearly- 

 Nautilus in the shell, quite as you supposed and exposed in your 

 first plate. It is, indeed, as if that plate was made from our ori- 

 ginal. The relative position of the different parts is consequently 

 the same as you fancied that it ought to be, and I am, indeed, 

 happy that I have the opportunity of giving such a confirmatory 

 statement. The only difference should be, that what you call the 

 ' dorsal fold' applied to the involute convexity of the shell has 

 not exactly the form and the position you ascribed to it. Ac- 

 cording to our observations, the mantle forms, at the basis of 

 what you said to be the hood or ligamentous disc {n, plate 1.), a 

 double fold, of which the superior part is thin and loose, the in- 

 ferior firm and connected with the mantle. This part forms a 

 sort of lip, and the whole fold is applied to the involute convexity 

 of the shell. I am afraid that this will not be completely clear, 

 but I hope that by our future plates our meaning shall be better 

 explained. For the moment this must be sufiicient. It shall 

 prove to you that the difference between what you said and what 

 we saw is very small. Perhaps a short indication will be quite 

 enough for the Journal." 



I am glad to be able to refer my friend to page 13 and plate 3. 

 fig. 1 . 2 of my memoir on the Pearly Nautilus, in which the part 

 of the double fold which he mentions as forming ' a sort of lip,' 

 is described and figured as the ' semilunar ridge from which 

 the mantle is continued to form the concave fold.' Thus the 

 supposed difference disappears. 



There is one important point in the anatomy of the Pearly 

 Nautilus to which the learned anatomists and naturalists of Hol- 

 land, in their notice of the specimen dissected by them, have not 



Ann. ^ Mag. N. Hist. Vol.xxi. Y 



