52 EXPLANATION OF PLATE 31. 



D. Transverse section across the Ink bag. 



d. First or upper plate. This plate is very thin, and 



smooth, and its structure is obscure, except on the 

 right marginal band at d', where the longitudinal 

 ridges on its surface are very distinct. 



e. Upper surface of second plate, marked with broad 



wavy lines, passing on each side from the axis out- 

 wards, across the body of the shaft, and over the 

 marginal bands. 



f. Upper surface of a third plate, exhibiting minute 



curved strise, ascending symmetrically in opposite 

 directions from each side of tlie axis of the shaft C, 

 and descending towards its margin. These curved 

 strise are intersected by minute longitudinal straight 

 lines, running nearly parallel to the axis of the 

 shaft. Towards the apex of the shaft aty^, the broad 

 transverse curves predominate over the fine longitu- 

 dinal fibres which lie beneath them. At g, no 

 transverse curves are visible.* (Mrs. Buckland. 

 Original.) 



Plate 31. V. I. p. 317. 



Fig. 1 . Animal of Nautilus Pompilius, fixed in its shell. 

 The shell is copied from one in the collection of Mr. 

 W. I. Broderip. (Animal from Owen. Shell ori- 

 ginal.) 



n. The Hood, or ligamento-muscular disk that surrounds 

 the head. 



p. The digital tentacles protruded from their sheaths. 



k. Funnel. 



a. b. c. d. e. Siphuncle. The desiccated membrane of 



* Herman von Meyer (Palaeologica, 1832, P. 322,) mentions the 

 occurrence of ink bags, together with the horny internal shells of 

 Sepia, (Onychoteuthis) in the Lias of Culmbach and Banz. 



