1.8" Flower-Like Sandstone Concretion - Pseudo Stromatolite
These concretions are frequently referred and marketed to as Stromatolite (trace fossils of algal colonies), but I'm pretty convinced that they are not. When cut and polished they do not show distinctive layering patterns you would expect to see in a Stromatolite. Also from reports on the location the flower like patterns are only seen on surface exposed specimens, indicating they are caused by erosion.
A concretion is a hard, compact mass of rock that forms around a nuclei and found in sedimentary rock. The initial nucleus that started the formation of the concretion is typically organic material. Concretions are typically spherical or oval but can take on some very irregular shapes too.