Darwin concluded that the sea level was high were it reached the mountain and as times passed sea level lowers down and clams were still on the mountain so when they died they were fossilized in the mountains. Hope this helps
They are female because they have two X chromosomes (as you can see at the bottom right of the picture) If they were male they would have one X chromosome and one Y chromosome.
The salt evaporates in the air thus when it hits the ground
