Everyone who wrote in got this one correct (I guess I made it too easy!)
Identification: This is a Capillaria egg.
What other parasite egg has a similar appearance and how can you differentiate it? Trichuris trichuria or whipworm eggs have a superficial appearance to Capillaria eggs, but do not have a striated shell and have much more prominent polar plugs.
Here are two the next to each other for comparison. I find the striated wall to be the most useful feature for identifying Capillaria eggs.
For those of you who are a little more advanced, you may be interested in the answer to Heather's question:
She asked whether it is possible to differentiate the eggs of Capillaria spp. The answer is YES: there are some subtle differences between the eggs of C. hepatica (such as the one shown) and those of C. philippinensis. Both can be found in the stool and have a striated cell wall, but C. philippinensis eggs are described as more "peanut" or "barrel" shaped with inconspicuous polar plugs, while C. hepatica eggs are more rounded and have more prominent polar plugs. C. hepatica eggs are also slightly larger (50-60 um) than C. philippinensis eggs(35-45 um). For comparison, T. trichuris eggs are 50-55um.