Amblema neislerii, the fat threeridge, is a freshwater mussel native to the rivers in southern Georgia and Florida. It belongs to the family Unionidae. It resides in shallow rivers in the muddy and sandy bottom of the river beds. It was named an endangered species in 1998 by state and federal agencies and it is now considered critically endangered. The mussel is usually less than four inches in length and also in its width. It possesses a dark brown to black outer shell. Its inner shell is bluish white to purple with an iridescent appearance. The shell is unique to mussels being inflated and also possessing approximately 7-9 prominent parallel ridges.