4 JEAN DAWSON. 



The funnel is lined with thick mucous membrane bearing sharp 

 conical teeth (Fig. 2). The teeth are arranged in a series of con- 

 centric loops, the crossed ends of which lie in the anterior portion 

 of the funnel (Figs. I and 2). The result of this arrangement is 

 that any radius drawn from the center of the mouth opening 

 strikes at least two teeth except over the posterior one fourth of 

 the circumference of the funnel. This posterior one fourth of 

 the funnel has teeth approximately on radii running from that 

 portion on the central loop which has an arc of the smallest 



P ' V' : -"'^ 1 *lC*^*iW>ii' J = r9 f< ' -V X 



'^^^y^&' ' 



I 



FIG. 2. Mouth of P. niarinus showing the arrangement of the teeth in concentric 

 loops. 



radius. This is a necessary result of the geometric relation of 

 the concentric loops (Figs. 2 and 3). The teeth on the .central 

 loop are so crowded that there are as many as on the larger outer 

 loop. These teeth are also larger and are grown together in 

 plates of two and more. 



The end of the tongue (Fig. i, Fig. 5 and Fig. 6) has two 

 lateral lobes (a) which are covered with smooth mucous mem- 

 brane and an anterior lobe (x) covered with plates of sharp teeth. 

 This free end of the tongue may be seen projecting for I or 2 

 mm. into the caudal end of the funnel and the teeth on its ante- 



