Anyone ever heard of "Vernal Crab"?

Back in January, I went digging in the mud for a baby crab for my aquarium. I found 3 of these little crabs about 1/2" wide. They were so small that they looked like spiders. I thought they were baby blue crabs. I put them in the aquarium and they moulted a couple of times and it was obvious that they were NOT blue crabs.... I only have one left and she is a survivor. She has moulted about 4 times and once when she moulted another crab mated with her. She had eggs and buried them in the sand. Then when her mate moulted, she ate his legs (all of them) and just left the body to die of starvation.... This is a mean species.. Anyway, she is mature at about 1' across and I am waiting to see if the babies become visible.... I looked on the internet and it is a small species of vernal crab.... Right now she is not displaying the tameness of Basket Case and does not like to interact with humans.