Fossils identification

A few days ago I went rock hunting, I collected some rocks but since I am not a geologist or paleontologist and have no experience as a fossil collector, therefore it is a little difficult to identify these rocks. Here is the first picture. If you know the name of the fossil and the estimated age or period please comment.

Fossil 1:

Fossil 2: This is a large rock, too big to take home.

Fossil 3: This is a large rock too.

Fossil 4:

Fossil 5:

Fossil 6: I thought this looked interesting because of the shape. Although it is broken, there is a distinguishable egg shape on these two embedded rocks.

These were collected in Texas. What is the theory behind these rocks? What do they tell about the area in the past? How old are they? Is it possible that during the living existence of these mollusks, bigger animals existed?

This is how the area looks like, can you see my truck?

Please share any information you may have about these rocks. Thank you very much.
I will post more pictures soon. This is my first post. I will try to improve in the near future.