Looks like a yellow scotch bonnet and is often confused for one by many gardeners. The Jamaican Mushroom has scotch bonnet style heat and a brilliant citrus flavor. Size is slightly larger than a scotch bonnet and is an annuum species, most obviously seen in the larger calyx, where the stem meets the fruit.
150000ish SHU. This is an estimate. Scoville ratings will change based on growing conditions.