2nd and 3rd finger
The 2nd digit consists of a flattened first phalanx and the last phalanx.
Next to the first joint of the 2nd digit sits the rudimentary phalanx of the 3rd finger. It is functionally merged with the 2nd finger and plays no independent role in the function of the wing. In penguins it is incorporated in the phalanx of the 2nd finger.
The second, last phalanx of the 2nd finger has a groove that holds the last primary. The remaining primaries are attached to the first phalanx and the carpometacarpus.