ODONTOPHORES OF WHELKS 61 



This creature's lingual band is divided 

 into five different areas, distinguishable by 

 the different characters of the teeth they 

 bear. 



The odontophore of the common whelk has 

 only three plates in each row, one carrying the 

 small central teeth and the two lateral ones 

 bearing the larger teeth. It is one of the most 

 fascinating for observational purposes. 



In the illustrations the odontophores of two 

 different whelks are shown, and it will be 

 noticed that there is a difference between them, 

 a difference that in the actual specimen could 

 not be detected but by the microscope. In 

 the central area of Fig. 11 there are six tiny 

 teeth in each horizontal row, but in Fig. 12 

 there are seven. Whether an abnormal con- 

 dition is here presented to us, or whether the 

 extra tooth per row in the median area is a 

 question of the creatures 7 comparative ages, we 

 must leave to the opinion of the marine 

 biologists. 



The radula of the English limpet (Patella 

 vulgata) is longer than the shell itself, and is 



