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VARIATIONS IN TEETH OF WHELK. 
JOHN IRVING, M.D., 
Scarborough, 
NEARLY seventy years ago microscopic examination and com- 
parison of teeth of glossophorous mollusca were suggested as 
important reliable aids to identification of species and their 
classification. Conchologists prefer, and are likely to adhere 
to, accepted shell methods rather than tackle the tedious 
process of dissecting out vadul@ and preparing them for observa- 
tion under the microscope. Nevertheless, in” variant forms, 
Photo=micrograph— Photo-micrograph— 
Central Teeth of Whelk. Lateral Teeth of Whelk. 
apparently allied, any doubt as to species might be definitively 
resolved by microscopic comparison of tooth-ribbons. Each 
species has, or is supposed to have, an odontophore, peculiar 
to itself, adapted to its mode of existence. Given any well- 
known mollusc, and another showing some external difference 
to it which involves a possible departure from type, investiga- 
tion of teeth ought to clear up the difficulty of decision. If 
vadulé are identical, species from which they are extracted 
are likewise identical notwithstanding divergence in shells. 
It should not be forgotten, however, that abnormalities may 
occur in microscopic teeth, or in the manner of their disposition, 
for which allowance ought to be made in exceptional instances. 
One of the best recognised tooth-ribbons is that of the 
Whelk, Buccinum undatum, whose teeth are usually illustrated 
tg1r Oct. 1. 
