Unfortunately, according to the information you provided, I can't determine the specific variety of this mushroom. However, according to the description of black mushrooms growing on toilet paper, it can be speculated that this mushroom may be bred by bacteria and fungi on toilet paper.
In order to ensure your health and safety, it is recommended not to eat this mushroom, clean the toilet in time and keep it clean and tidy. If you have any questions or concerns, it is recommended to consult a professional doctor or mushroom expert.