306 Rev. M. J. Berkeley's Anatomy of 



different vessels which expose the blood to the action of the air, are 

 spread, is so extremely transparent that a clear view is obtained of the 

 contents of the cavity without making any incision ; it has (at least 

 in specimens preserved in spirits) a slight degree of rigidity and elasticity, 

 like the shell which protects it; and perhaps this circumstance 

 compensates in some measure for its extreme thinness. So much is this 

 the case, that even when the shell is removed, it is able in general to 

 support itself without falling down like the flaccid membrane of Pulmo- 

 nifera in general. 



The mass of the moulh is oval, and has the upper lip furnished with 

 a horny crescent-shaped plate, which has a single projecting tooth in the 

 center as in Limax, and not numerous toothlets as in Helix. 



The mass itself has a flat forked muscular strap shaped like the letter 

 Y, attached to it behind, embracing its under-side firmly with the two 

 arms, which shortly after become confluent, and the single strap formed 

 by this confluence is inserted into the foot behind. By means of this 

 muscle the mass is retracted, together with a portion of the skin imme- 

 diately surrounding the mouth itself. Above the muscle between its 

 arms, the cartilaginous cone of the tongue makes a slight projection. 

 The tongue itself which hues the bottom of the cavity of the mass, or 

 rather of an organ fixed to it, which performs the function of a lower 

 lip, is most beautifully and regularly chequered in parallel, transverse 

 and longitudinal lines, formed by most minute subtriangular plates or 

 spiculae, whose points are directed backwards exactly as in Helix 

 (aspersa.J 



Immediately above the cone is the commencement of the oesophagus ; 

 on each side of which the salivary ducts enter into the mass; and above 

 these the upper ganglions of the nervous cord, for the mass is evidently 

 formed of two confluent ganglions ; each gives off a nerve to the large 

 tentaculum on its own side ; and above a nerve forked soon afl;er its origin 

 proceeding to the upper part of the mass of the mouth. The lower 

 ganglion, connected on each side by a cord with the central ganglions is 

 large and nearly circular, giving off nerves on all sides, as in Helix. The 

 oesophagus, as usual, passes through the circle formed by the junction. 



The (Esophagus is soon confounded with the stomach which is a 

 membraneous dilatation, consisting of two parts. The salivary glands 



