- skull small, length less than 5 cm (2 in) *
- molars with w-shaped ridge (blue) on top
- skull large, length greater than 3 cm (1.2 in) *
- molars without w-shaped ridge on top
* These size ranges overlap, if you have a skull that is 3 – 5 cm (1.2 – 2 in) in length then you must use Part B of this step.