214 



THE AMERICAN NATURALIST. [Vol. XXXVIII. 



found on the anterior part of the plate, having 

 a triangular form. The size 

 and prominence of the teeth 

 gradually decreases toward 

 the posterior part of the 

 plate. This gradual increase 

 in size of the teeth and the 

 ridges indicates how both are - -one <,f the 

 continually forming to take 't'a',"elrs 

 the place of the more anterior from a protiie view, 

 ones as they become worn ^ 

 jest teeth are those found on the smallest 

 t is difificult to be certain that teeth 



ig structure but one that is difficult 

 When this organ is removed from 

 lewhat triangular in shape (Fig. 6). In the 

 )r part there is a single row of teeth, having 

 a broad free margin and ter- 

 minating at each side in a 

 rather broad blunt process 

 (Fig. 7). There are an in- 

 definite number of long, slen- 

 der, sharp teeth arranged in 

 rows which correspond to the 

 teeth of the median ridge. 

 The bases of these lateral 

 teeth are imbeded in the 

 muscles of the radula (Fig. 

 8). Each lateral tooth is 

 bent at an angle of about 90 

 degrees. This arrangement 

 of the teeth would give the 

 following formula for //. soli- 

 ■ntobioc. taria cc. I cc. 

 d,.u..„g. gcnita/ ori^yrm:— This 



system of organs is fully dis- 

 been able to demonstrate of all the 



