In 1869 many chemists did not agree with mendeleev's periodic table. three reasons why.

1) The position of isotypes couldn't be explained
2. Wrong order of atomic masses of some elements couldn't be explained and he arranged them in order of increasing atomic masses. 
3)A correct position could NOT be assigned to hydrogen.
I think those are 3 anomalies to the table

Usually this mountain-building process produces majestic peaks and steep slopes. you should look for these along the other features.