MOLLUSCA. 55 



86. A Calamary (Loligo vulgaris), dissected to shew it-> 

 internal skeleton, the 'gladius' or 'pen.' The 'gladius' ex- 

 tends throughout the whole length of the dorsal portions of the 

 mantle. It is of a horny texture, dark in colour, and consists 

 of a median shaft with two lateral alse. It lies loosely in the 

 cavity, so as easily to fall out when the integument is cut 

 away. This species represents the family Teuthidce. 



87. A Sepia (Sepia officinalis), dissected to shew the posi- 

 tion of the internal skeleton, or ( cuttle-bone.' The ' cuttle- 

 bone ' is imbedded in the dorsal integument. It is a light, 

 cellular, calcareous body, peculiarly characteristic of the genus 

 Sepia. Its form is an elongated oval, convex, and marked by 

 a slight median keel on the dorsal surface, and partly convex and 

 partly concave on the ventral surface. The margin of the 

 ' bone ' is seen to be more or less horny, and darker in colour. 

 This species represents the family Sepiadce. 



88. Portion of 'cuttle-bone' from a Sepia, treated with 

 acid to remove the earthy matter, and shew the laminated 

 structure of the residual animal matter. 



89. The lips and jaws of a Sepia (Sepia officinalis). 



A portion of the lips has been removed, and a black and 

 white bristle passed through the mouth into the oesophagus. 



The lip, which surrounds the mouth loosely, is beset with 

 numerous elongated papillae. The jaws consist of two horny 

 beaks of a brown colour, in shape not unlike those of a parrot. 

 They are embedded in a mass of muscular fibres by which the 

 movements of the jaws are regulated. The margin of the lower 

 one overlaps that of the upper. Between them is seen the 

 tongue with its serrated surface. From the hinder portion of 

 the buccal mass the oesophagus may be seen passing downwards 

 through the cartilaginous ring towards the stomach. 



90. A Cuttlefish (Eledone), dissected to shew its digestive, 

 respiratory, circulatory, and generative organs. 



The bag containing the viscera has been laid open, and the 

 mantle pinned back. An incision has been carried through the 

 cartilaginous ring at the base of the tentacles and the muscular 

 mass surrounding the jaws, so as to expose the origin of the 

 oesophagus. This is a narrow tube, which, after a course of 

 uniform diameter for about an inch, suddenly expands into a 



