250 ^'EW YORK STATE MUSEUM 



four divisions, of which tlie two lesser are situated above the two 

 larger divisions. The lateral lips are each entire, comparatively 

 large and somewhat crescentiform. 



The mouth leads into an organ known as the buccal body (pi. 

 4, fig. 1). This organ is somewhat irregularly oval-shaped, and 

 contains the masticatory organ known as the radula (pi. 4, fig. 3). 



Just within the upper lip is the crescentif orm, corneous lamina, 

 known as the " jaw " (pi. 5, fig. 2), reddish brown in color, and 

 occupying the position of an upper jaw. On the outer face of the 

 jaw are 12 vertical ridges, with pointed ends, which project be- 

 yond the lamina. The ridges with their pointed ends closely 

 resemble teeth. The jaw is attached to the buccal body by a 

 band of muscular fibers, inserted in its upper convex edge. Dur- 

 ing feeding the jaw projects beyond the lips, which are protruded, 

 having the appearance of a prehensile proboscis, which takes 

 hold of the food and draws It to the mouth, the jaw cutting it into 

 small pieces, acting as a chopping knife. 



The food now passes into the buccal body. A reference to the 

 figures on plate 4 will give a clear idea of the structure of that 

 organ. The outer walls are thick and are composed of constrictor 

 muscular fibers. On the floor of this organ are two gristly ele- 

 vations, known as the odontophoral cartilages, which have, at- 

 tached to their lower parts, small muscles arising from the side 

 walls of the buccal body. Resting on the odontophoral cartilages 

 is a cushion-shaped elevation, inclosed in a mucous membrane, 

 known as the odontophore. Overlying this is the lingual ribbon, 

 or radula, which is studded with an immense number, some fifteen 

 thousand, of small teeth or denticles, arranged in transverse and 

 longitudinal rows. 



The teeth preserve the same form throughout in a longitudinal 

 line. The central line always differs from the others, and they 

 gradually vary in form and size, as they pass from the central 

 line laterally. The radula, or lingual ribbon, takes its origin in 

 the sac of the radula (pi. 4, fig. 3, 4), which projects from the 

 lower posterior part of the buccal body, continuing anteriorly 

 from the radular sac upward to the dorsal part of the buccal body. 



